Fix release notes markdown
Fix release notes markdown

Links should use []() instead of ()[].

PiperOrigin-RevId: 423073748

amzn/exoplayer-amazon-port,androidx/media,google/ExoPlayer,google/ExoPlayer,androidx/media,google/ExoPlayer,androidx/media,amzn/exoplayer-amazon-port,amzn/exoplayer-amazon-port