SDK / exoplayer

Note that this removes a workaround for malformed content, in which the
track_ID is set incorrectly. It's unclear there was sufficient reason to
implement that workaround, and so it's preferable to remove it, rather
than implementing the concept of unrecognized tracks, which would be
needed to keep it and to also fix this issue.

Issue: #9056
#minor-release
PiperOrigin-RevId: 379506261