Remove app-specific build configurations recommendations from dev-guide and readme
Remove app-specific build configurations recommendations from dev-guide and readme

Issue:#5572
PiperOrigin-RevId: 238401862

google/ExoPlayer,superbderrick/ExoPlayer,amzn/exoplayer-amazon-port,saki4510t/ExoPlayer,saki4510t/ExoPlayer,stari4ek/ExoPlayer,stari4ek/ExoPlayer,superbderrick/ExoPlayer,saki4510t/ExoPlayer,google/ExoPlayer,ened/ExoPlayer,stari4ek/ExoPlayer,androidx/media,ened/ExoPlayer,ened/ExoPlayer,androidx/media,amzn/exoplayer-amazon-port,androidx/media,google/ExoPlayer,superbderrick/ExoPlayer,amzn/exoplayer-amazon-port