Mux-python

- **breaking change**: the `max_channel_layout` field of `Track` was an enum and is now an open string, as our internal implementation couldn't realistically and exhaustively enumerate all possible options. This should be a very small change that applies only to projects ingesting media with multi-channel, non-stereo audio (5.1, 7.1, etc.).

- minor doc updates; check the [API reference](https://docs.mux.com/api-reference) for more

- [Live Captions](https://docs.mux.com/guides/video/add-live-captions) is now GA!
- Minor API documentation fixes; consult [the API reference](https://docs.mux.com/api-reference) for full details.

- added operation `get-live-stream-playback-id`; consult https://docs.mux.com/api-reference for up-to-date details on our API

- Fixed typo in `RealTimeBreakdownValue` such that `concurrent_viewers` is correctly represented. Thanks to catlina71 for the report.

- Low latency (public beta) has landed! https://docs.mux.com/guides/video/reduce-live-stream-latency#lower-latency-options
- Minor API updates; consult https://docs.mux.com/api-reference for our canonical API reference.