Refactor FXIOS-12796 [Swift 6 Migration] Fix Swift 6 errors in Client unit tests for FormAutofillHelperTests

[ih-codes]

📜 Tickets

Jira ticket
Github issue

💡 Description

• Fixes Swift 6 errors in FormAutofillHelperTests

cc @Cramsden @lmarceau @dataports

📝 Checklist

• I filled in the ticket numbers and a description of my work
• I updated the PR name to follow our PR naming guidelines
• I ensured unit tests pass and wrote tests for new code
• If working on UI, I checked and implemented accessibility (Dynamic Text and VoiceOver)
• If adding telemetry, I read the data stewardship requirements and will request a data review
• If adding or modifying strings, I read the guidelines and will request a string review from l10n
• If needed, I updated documentation and added comments to complex code

[mobiletest-ci-bot]

💪 Quality guardian

1 tests files modified. You're a champion of test coverage! 🚀

🧹 Tidy commit

Just 1 file(s) touched. Thanks for keeping it clean and review-friendly!

🙌 Friday high-five

Thanks for pushing us across the finish line this week! 🙌

✅ Per-file coverage

All changed files meet the threshold of 35.0%.

Generated by 🚫 Danger Swift against 5f9e8ff

[github-actions]

🚀 PR merged to main, targeting version: 146.1