In some cases the codec selected for decoding has a different MIME type than
the media. In thoses cases Transformer continued to use the media's MIME type
and that caused codec configuration failures.
Removed `EncoderUtil.findCodecForFormat()` as we stopped using the method it
uses for finding a codec. Plus, the method is only used in the test.
See also `MediaCodecUtil.getALternativeCodecMimeType()`.
PiperOrigin-RevId: 536683663
(cherry picked from commit fedd99b4911e61f18e68e57021ac8b55db7e5f44)
