Remove self-links, and remove section that is documenting internal ordering behaviour of [`SimpleBasePlayer.getCombinedMediaMetadata`](https://github.com/google/ExoPlayer/blob/bb270c62cf2f7a1570fe22f87bb348a2d5e94dcf/library/common/src/main/java/com/google/android/exoplayer2/SimpleBasePlayer.java#L1770) rather than anything specifically about this method. #minor-release PiperOrigin-RevId: 490923719 (cherry picked from commit ed8c196e)
