12 hour time is not 12 hour on british english localisation

[fluxbug-flutter]

Steps to reproduce

1. go to settings > language and time and set the app language to british english
2. set the time format to 12 hour
3. take note of the times listed there(they're all 24 hour time)
4. go to a message posted after mid day and look at the time listed

Expected behaviour

the time of messages and the time in the settings should be 12 hour time such as "2:00 PM"

Actual behaviour

the time of messages sent and the example in the settings is in 24 hour time such as "14:00"

Client and system settings

Version 1.0.0, Beta 59, Channel Beta, Build 2400, Android 16 (arm64), Device samsung SM-S928B, Locale en-GB, Push fcm, Flutter 3.47.2, Dart 3.13.2

Stances

Approvals

• CR - Version 1.0.0, Beta 60, Channel Beta, Build 67, iOS 26.6 (arm64), Device iPhone13,1, Locale en-GB, Push apns, Flutter 3.47.2, Dart 3.13.2
• CR: Version 1.0.0, Channel Canary, Build 2404, Android 15 (arm64), Device OnePlus CPH2465, Locale en-GB, Push fcm, Flutter 3.47.2, Dart 3.13.2

Denials

None

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Reported: #1565