This aligns the behavior with `MediaExtractor`, which sets this key in its [`MediaFormat`](https://developer.android.com/reference/android/media/MediaExtractor#getTrackFormat(int)) output.
Additionally, unnecessary `selectTrack` calls have been removed from the existing `getTrackFormat_...` tests, as they are not required to fetch the track format.
PiperOrigin-RevId: 700741326