### Description
Remove Android 5 support. For supporting Chromecast playback via media3,
we need to upgrade the media3 library. This library no longer supports
Android 5, so we need to bump our minimum version as well. Only 0.13% of
our Google Play users are still on this ancient Android version released
in 2014. Dropping support seems okay now, especially considering that no
one should expose such an old device to the internet anymore. The app
will continue to work on Android 5 but will not receive updates anymore.
### Checklist
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