fix(TMCU-1048): Remove redundant useElevatedSurface from MMDS BottomSheet callsites (#33159)

<!-- CURSOR_AGENT_PR_BODY_BEGIN -->
## **Description**

MMDS `BottomSheet` now handles pure-black elevated surface styling
internally. This PR removes the redundant `useElevatedSurface()` shim
and `twClassName` prop from the two remaining accounts-engineer
callsites scoped in TMCU-1048.

**Changes:**
- `ConfirmTurnOnBackupAndSyncModal` — removed `useElevatedSurface`
import/usage and `twClassName` on `BottomSheet`
- `LearnMoreBottomSheet` — removed `useElevatedSurface` import/usage and
`twClassName` on `BottomSheet`

## **Changelog**

CHANGELOG entry: null

## **Related issues**

Fixes: TMCU-1048

## **Manual testing steps**

```gherkin
Feature: Pure black elevated surface on MMDS BottomSheet

  Scenario: Backup and sync confirm sheet renders with correct surface
    Given the app is in dark mode with pure black preview enabled
    When the user opens the backup and sync confirmation bottom sheet
    Then the bottom sheet surface should use the elevated background (not collapse into pure black)

  Scenario: Multichain intro learn-more sheet renders with correct surface
    Given the app is in dark mode with pure black preview enabled
    When the user opens the multichain accounts learn-more bottom sheet
    Then the bottom sheet surface should use the elevated background (not collapse into pure black)
```

N/A for automated cloud-agent environment — visual QA requires
device/simulator with pure black preview enabled.

## **Screenshots/Recordings**

N/A — visual surface change only; requires device QA with pure black
preview enabled per acceptance criteria.

### **Before**

N/A

### **After**

Backup and Sync BottomSheet background color still works as expected

<img width="403" height="374" alt="Screenshot 2026-07-13 at 11 25 33 AM"
src="https://github.com/user-attachments/assets/6b74972e-712c-43b1-a2a9-1d9bdf32782a"
/>


## **Pre-merge author checklist**

- [x] I've followed [MetaMask Contributor
Docs](https://github.com/MetaMask/contributor-docs) and [MetaMask Mobile
Coding
Standards](https://github.com/MetaMask/metamask-mobile/blob/main/.github/guidelines/CODING_GUIDELINES.md).
- [x] I've completed the PR template to the best of my ability
- [x] I've included tests if applicable
- [x] I've documented my code using [JSDoc](https://jsdoc.app/) format
if applicable
- [x] I've applied the right labels on the PR (see [labeling
guidelines](https://github.com/MetaMask/metamask-mobile/blob/main/.github/guidelines/LABELING_GUIDELINES.md)).
Not required for external contributors.

#### Performance checks (if applicable)

- [ ] I've tested on Android
  - Ideally on a mid-range device; emulator is acceptable
- [ ] I've tested with a power user scenario
- Use these [power-user
SRPs](https://consensyssoftware.atlassian.net/wiki/spaces/TL1/pages/edit-v2/401401446401?draftShareId=9d77e1e1-4bdc-4be1-9ebb-ccd916988d93)
to import wallets with many accounts and tokens
- [ ] I've instrumented key operations with Sentry traces for production
performance metrics
- See [`trace()`](/app/util/trace.ts) for usage and
[`addToken`](/app/components/Views/AddAsset/components/AddCustomToken/AddCustomToken.tsx#L274)
for an example

## **Pre-merge reviewer checklist**

- [ ] I've manually tested the PR (e.g. pull and build branch, run the
app, test code being changed).
- [ ] I confirm that this PR addresses all acceptance criteria described
in the ticket it closes and includes the necessary testing evidence such
as recordings and or screenshots.
<!-- CURSOR_AGENT_PR_BODY_END -->

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Co-authored-by: Cursor Agent <cursoragent@cursor.com>
Co-authored-by: George Marshall <georgewrmarshall@users.noreply.github.com>

Author: georgewrmarshall

app/components/UI/Identity/ConfirmTurnOnBackupAndSyncModal/ConfirmTurnOnBackupAndSyncModal.tsx

@@ -15,15 +15,12 @@ import { ConfirmTurnOnBackupAndSyncModalNavigateParams } from '../BackupAndSyncT
 import { InteractionManager } from 'react-native';
 import useThunkDispatch from '../../../hooks/useThunkDispatch';
 
-import { useElevatedSurface } from '../../../../util/theme/themeUtils';
-
 const ConfirmTurnOnBackupAndSyncModal = () => {
   const bottomSheetRef = useRef<BottomSheetRef>(null);
   const { enableBackupAndSync, trackEnableBackupAndSyncEvent } =
     useParams<ConfirmTurnOnBackupAndSyncModalNavigateParams>();
 
   const dispatch = useThunkDispatch();
-  const surfaceClass = useElevatedSurface();
 
   const enableBasicFunctionality = async () => {
     await dispatch(toggleBasicFunctionality(true));
@@ -54,7 +51,7 @@ const ConfirmTurnOnBackupAndSyncModal = () => {
   };
 
   return (
-    <BottomSheet ref={bottomSheetRef} twClassName={surfaceClass}>
+    <BottomSheet ref={bottomSheetRef}>
       <ModalContent
         title={turnContent.bottomSheetTitle}
         message={turnContent.bottomSheetMessage}

app/components/Views/MultichainAccounts/IntroModal/LearnMoreBottomSheet.tsx

@@ -22,7 +22,6 @@ import { RootState } from '../../../../reducers';
 import { useDispatch, useSelector } from 'react-redux';
 import { setMultichainAccountsIntroModalSeen } from '../../../../actions/user';
 import { LEARN_MORE_BOTTOM_SHEET_TEST_IDS } from './LearnMoreBottomSheet.testIds';
-import { useElevatedSurface } from '../../../../util/theme/themeUtils';
 
 interface LearnMoreBottomSheetProps {
   onClose?: () => void;
@@ -40,7 +39,6 @@ const LearnMoreBottomSheet: React.FC<LearnMoreBottomSheetProps> = ({
   const isBasicFunctionalityEnabled = useSelector(
     (state: RootState) => state?.settings?.basicFunctionalityEnabled,
   );
-  const surfaceClass = useElevatedSurface();
 
   const handleBack = useCallback(() => {
     sheetRef.current?.onCloseBottomSheet();
@@ -68,7 +66,6 @@ const LearnMoreBottomSheet: React.FC<LearnMoreBottomSheetProps> = ({
       ref={sheetRef}
       onClose={onClose}
       testID={LEARN_MORE_BOTTOM_SHEET_TEST_IDS.BOTTOM_SHEET}
-      twClassName={surfaceClass}
     >
       <View style={styles.container}>
         <View style={styles.header}>