This was causing state pollution in the new selection. I can't see why
this needs to happen when a selection changes to another.
This fixes https://github.com/ppy/osu/issues/30839 and also the same
issue happening for the new combo toggle.
Tests all seem to pass, and I can't immediately find anything broken,
but YMMV.
Though the code appears slightly different, it should be semantically
equivalent. APIUser equality is implemented on `Id` and `Host` should
never transition from non-null to null.
This one is super duper annoying to test, because we already have e.g.
`TestScenePlaylistsScreen`. The only way to test it would be to use an
`OsuGameTestScene`.
Maybe this is okay?