Summary of Changes

• Similar to Solana, we need to strip the Error: prefix that Webkit applies when responding to a request or we lose the json formatting.

This pull request fixes #7392

Submitter Checklist:

• Unit Tests are updated to cover new or changed functionality
• User-facing strings use NSLocalizableString()
• New or updated UI has been tested across:
  • Light & dark mode
  • Different size classes (iPhone, landscape, iPad)
  • Different dynamic type sizes

Test Plan:

1. Visit Brave Talk with a Premium account
2. Connect your wallet to Brave Talk
3. Tap Host a Web3 Call
4. Tap cancel on the signature request
5. Verify error is displayed as Sign request cancelled instead of messy formatting (see issue).

If you have Brave Talk Premium, please verify the fix is working there.
This can also be verified using Ethereum Test DApp.

1. Visit https://metamask.github.io/test-dapp/
2. Connect your wallet to the test DApp
3. Tap Sign under Personal Sign.
4. Tap cancel on the signature request
5. Verify Sign button now displays ERROR: THE USER REJECTED THE REQUEST
   • Previously: ERROR: ("CODE": 4001, 'MESSAGE": "THE USER REJECTED THE REQUEST.)

Screenshots:

Reviewer Checklist:

• Issues include necessary QA labels:
  • QA/(Yes|No)
  • bug / enhancement
• Necessary security reviews have taken place.
• Adequate unit test coverage exists to prevent regressions.
• Adequate test plan exists for QA to validate (if applicable).
• Issue and pull request is assigned to a milestone (should happen at merge time).