Revert "Move CEA-608/708 to list of supported HLS features (#1465)"

This reverts commit 417e222.

README.md

@@ -85,13 +85,13 @@ HLS features supported:
  - ISO-BMFF / MP4 / CMAF support
  - MPEG-2 TS support (transmuxing provided by [mux.js][] v4.4+, must be separately included)
  - WebVTT and TTML
- - CEA-608/708 captions
 
 HLS features **not** supported:
  - Encrypted content with FairPlay: https://github.com/google/shaka-player/issues/382
  - Encrypted content with PlayReady: https://github.com/google/shaka-player/issues/1145
  - Key rotation: https://github.com/google/shaka-player/issues/917
  - I-frame-only playlists: https://github.com/google/shaka-player/issues/742
+ - CEA-608/708 captions: https://github.com/google/shaka-player/issues/276
  - Raw AAC (without an MP4 container): https://github.com/google/shaka-player/issues/1083
 
 [mux.js]: https://github.com/videojs/mux.js/releases