This change is a no-op, because
`SubtitleTranscodingExtractorOutput.seekMap` forwards directly to the
delegate implementation, but it seems clearer to always use the
wrapper.
Also remove a no-op assignment in `MatroskaExtractor`.
This is a follow-up to Issue: androidx/media#1779 where I manually checked every
implementation of `Extractor.init` for a similar mistake.
#cherrypick
PiperOrigin-RevId: 683607090
abfeea518e