build(User/Account): update deprecation notes and add to overrides

[joshtrichards]

Addresses lint warnings like these:

w: file:///home/runner/work/android/android/app/src/main/java/com/nextcloud/client/account/AnonymousUser.kt:52:18 This declaration overrides a deprecated member but is not marked as deprecated itself. Add the '@Deprecated' annotation or suppress the diagnostic.
w: file:///home/runner/work/android/android/app/src/main/java/com/nextcloud/client/account/AnonymousUser.kt:54:18 This declaration overrides a deprecated member but is not marked as deprecated itself. Add the '@Deprecated' annotation or suppress the diagnostic.
w: file:///home/runner/work/android/android/app/src/main/java/com/nextcloud/client/account/MockUser.kt:47:18 This declaration overrides a deprecated member but is not marked as deprecated itself. Add the '@Deprecated' annotation or suppress the diagnostic.
w: file:///home/runner/work/android/android/app/src/main/java/com/nextcloud/client/account/MockUser.kt:49:18 This declaration overrides a deprecated member but is not marked as deprecated itself. Add the '@Deprecated' annotation or suppress the diagnostic.
w: file:///home/runner/work/android/android/app/src/main/java/com/nextcloud/client/account/RegisteredUser.kt:33:16 'fun <T : Parcelable!> readParcelable(p0: ClassLoader?): T?' is deprecated. Deprecated in Java.
w: file:///home/runner/work/android/android/app/src/main/java/com/nextcloud/client/account/RegisteredUser.kt:34:16 'fun <T : Parcelable!> readParcelable(p0: ClassLoader?): T?' is deprecated. Deprecated in Java.
w: file:///home/runner/work/android/android/app/src/main/java/com/nextcloud/client/account/RegisteredUser.kt:35:16 'fun <T : Parcelable!> readParcelable(p0: ClassLoader?): T?' is deprecated. Deprecated in Java.
w: file:///home/runner/work/android/android/app/src/main/java/com/nextcloud/client/account/RegisteredUser.kt:44:18 This declaration overrides a deprecated member but is not marked as deprecated itself. Add the '@Deprecated' annotation or suppress the diagnostic.
w: file:///home/runner/work/android/android/app/src/main/java/com/nextcloud/client/account/RegisteredUser.kt:46:18 This declaration overrides a deprecated member but is not marked as deprecated itself. Add the '@Deprecated' annotation or suppress the diagnostic.

Also makes the deprecation notice a bit more informative.

🖼️ Screenshots

🏚️ Before	🏡 After
B	A

🏁 Checklist

• Tests written, or not not needed

[github-actions]

APK file: https://www.kaminsky.me/nc-dev/android-artifacts/16483.apk



To test this change/fix you can simply download above APK file and install and test it in parallel to your existing Nextcloud app.

[github-actions]

blue-Light-Screenshot test failed, but no output was generated. Maybe a preliminary stage failed.