Refactor FXIOS-15359 [Technical Debt] [Redux] Use @CopyWithUpdates macro for NativeErrorPageState

[satomasahiro2005]

📜 Tickets

Jira ticket
Github issue

💡 Description

Applies the @CopyWithUpdates Swift macro to NativeErrorPageState, replacing manual state construction in the reducer and defaultState with state.copyWithUpdates(...) calls.

Only properties that change need to be passed, reducing boilerplate. For reference, see #32214 which applied the same pattern to HomepageState.

No UI, telemetry, or string changes are included in this PR.

🎥 Demos

📝 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]

	Messages
📖	Project coverage: 41.03%

🧹 Tidy commit

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

💬 Description craftsman

Great PR description! Reviewers salute you 🫡

✅ New file code coverage

No new file detected so code coverage gate wasn't ran.

Client.app: Coverage: 39.45

File	Coverage
NativeErrorPageState.swift	92.73%	✅

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