Remove legacy timezone handling

[david-allison]

• Follow-on from Remove new timezone handling setting Anki-Android#15746

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• schedTimingTodayLegacy
• localMinutesWestLegacy

Mostly upstream: https://github.com/ankitects/anki/blob/main/rslib/src/backend/ankidroid.rs

[Sanjai-Shaarugesh]

✨ Fix: Timestamp Handling in AnkiDroid Backend Functions (#369)

This PR improves the timestamp handling logic in the AnkiDroid backend functions to ensure consistent and accurate parsing across operations.

🔧 What’s Fixed

• Resolved inconsistencies in timestamp parsing logic.
• Improved compatibility with AnkiDroid’s expected formats.

🔗 Related Work

This fix builds on the foundation laid in PR #3899, refining and adapting it specifically for the AnkiDroid backend.