Removes subtitle allow-list by using SubtitleDecoderFactory.DEFAULT.
When the format is unsupported, the extractor registers one track and
sends the format with the Format#sampleMimeType set to TEXT_UNKNOWN and
Format#codecs field set to the actual subtitle MIME type.
The TextRenderer will recognize this MIME Type as not supported which is
gonna be visible in the event log.
PiperOrigin-RevId: 400679058
