Add documentation for test dependency groups on mobile platforms.

[freakboy3742]

The documentation for test groups doesn't list configuration options for iOS or Android.

It turns out that because of the way test-groups is handled (by rolling dependencies in to test-requires), it works fine on both iOS and Android, and the settings files are already populated. I can only assume this was an oversight on my part when I wrote the iOS docs, which @mhsmith inherited by doing a "search for _IOS and add the same change for Android" when he added Android support.

This pull request proves that test-groups works on iOS and Android with cibuildwheel 3.1.4.

[henryiii]

There shouldn’t be any problem switching to -—group either, now that pip and uv support it?

[freakboy3742]

There shouldn’t be any problem switching to -—group either, now that pip and uv support it?

Do you mean switching to using --group explicitly, rather than the "roll test-depends into the test-requires" approach that is currently being used? If that's the case, then yes, it should be possible for pip on iOS. uv doesn't support iOS at this time, so it's a moot point there.