fix: fixed TokenList crash when changing networks (#27655)

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## **Description**
Fixes a crash in the `TokenList` component when switching networks.

### Cause of Bug
useLayoutEffect with recomputeViewableItems() fires synchronously after
FlashList's own useLayoutEffect truncates its internal layouts array to
match the new (shorter) data. But FlashList's ViewabilityHelper still
holds possiblyViewableIndices from the old (longer) data — those only
get reset later via computeItemViewability() in a useEffect. So
recomputeViewableItems() iterates stale indices, calls getLayout(index)
where index >= layouts.length, and FlashList throws "index out of
bounds, not enough layouts".

### Bug Fix
Remove the useLayoutEffect. This is safe because extraData already
includes isTokenNetworkFilterEqualCurrentNetwork, which triggers
FlashList to re-render and internally recompute viewability with valid
indices on its own schedule.

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## **Changelog**

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CHANGELOG entry: fix TokenList crash when switching networks

## **Related issues**

Fixes:
#27651 (comment)

## **Manual testing steps**

```gherkin
Feature: Token list stability on network switch

  Scenario: user switches network on "Cash" or "Tokens" token list without crash
    Given user is on the token list full view with tokens visible

    When user switches network filter (e.g. "Popular Networks" to "Linea")
    Then the token list updates without crashing

  Scenario: user switches network on Tokens full view without crash
    Given user is on the token list full view with multiple tokens visible

    When user switches network filter
    Then the token list updates without crashing
```

## **Screenshots/Recordings**

<!-- If applicable, add screenshots and/or recordings to visualize the
before and after of your change. -->

### **Before**

<!-- [screenshots/recordings] -->
<img width="1206" height="2622" alt="image"
src="https://github.com/user-attachments/assets/ffe6255f-43c5-4f64-bee7-2b8f03106681"
/>

### **After**

<!-- [screenshots/recordings] -->


https://github.com/user-attachments/assets/21d332be-13b6-4e2a-a378-2a1afa1a54c5

## **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.

## **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_SUMMARY -->
---

> [!NOTE]
> **Low Risk**
> Small UI lifecycle change limited to `TokenList`; risk is low but
could affect how quickly FlashList updates viewability after
network/filter changes.
> 
> **Overview**
> Prevents a crash when changing networks by removing the
`useLayoutEffect` that forced `FlashList` to call
`recomputeViewableItems()` when the token network filter/current network
equality changed.
> 
> This also drops the unused `useLayoutEffect` import, leaving list
updates to normal `FlashList` rendering and `extraData` updates.
> 
> <sup>Written by [Cursor
Bugbot](https://cursor.com/dashboard?tab=bugbot) for commit
67fa172. This will update automatically
on new commits. Configure
[here](https://cursor.com/dashboard?tab=bugbot).</sup>
<!-- /CURSOR_SUMMARY -->

Author: Matt561

app/components/UI/Tokens/TokenList/TokenList.tsx

@@ -1,6 +1,5 @@
 import React, {
   useCallback,
-  useLayoutEffect,
   useRef,
   useMemo,
   useEffect,
@@ -84,10 +83,6 @@ const TokenListComponent = ({
   const navigation = useNavigation();
   const { trackEvent, createEventBuilder } = useAnalytics();
 
-  useLayoutEffect(() => {
-    listRef.current?.recomputeViewableItems();
-  }, [isTokenNetworkFilterEqualCurrentNetwork]);
-
   // Apply maxItems limit if specified
   const displayTokenKeys = useMemo(
     () => (tokenKeys || []).slice(0, maxItems || undefined),