chore: remove unused ContractBox temp components (#29816)

## **Description**

Removes the unused temporary ContractBox and ContractBoxBase components
from `app/component-library/components-temp/Contracts`.

The prior audit found no production imports, and a follow-up reference
search confirms no remaining references.

## **Changelog**

CHANGELOG entry: null

## **Related issues**

Fixes:

## **Manual testing steps**

```gherkin
Feature: temporary component cleanup

  Scenario: ContractBox temp components are removed
    Given the repository is on this branch
    When searching for ContractBox and ContractBoxBase references
    Then no app, test, or Storybook references are found
```

## **Screenshots/Recordings**

N/A. Code cleanup only.

### **Before**

N/A

### **After**

N/A

## **Validation**

- `rg -n
"ContractBox|ContractBoxBase|CONTRACT_BOX|components-temp/Contracts" app
tests .storybook --glob '!node_modules/**'` returned no matches.
- `yarn lint:tsc` was run and failed on existing unrelated type errors
in confirmations, SocialLeaderboard tests, bridge messenger types,
multichain assets rates messenger types, and test account utilities.

## **Pre-merge author checklist**

- [ ] 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
- [ ] 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
- [ ] I've tested with a power user scenario
- [ ] I've instrumented key operations with Sentry traces for production
performance metrics

## **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.

Author: AndyMBridges