Upgrade Android Gradle Plugin

Upgrading Android Gradle Plugin (AGP) is kind of blocked by a bug introduced in lint in version 8.11: https://issuetracker.google.com/issues/432144179
Two possibilities:
- wait for the bug to be fixed
- disable lint

Also to be considered: F-droid doesn't seem to support AGP 8.12 for now: https://gitlab.com/fdroid/admin/-/issues/593