Native livestreaming was previous deprecated and has now been removed.
We kept the 2 livestream options, now both using WebRTC livestreaming

LIVESTREAM=1 can now be used for WebRTC streaming over a public network
LIVESTREAM=2 can be used for WebRTC streaming over a local or private
network.

- New feature (non-breaking change which adds functionality)
- Breaking change (fix or feature that would cause existing
functionality to not work as expected)
- This change requires a documentation update

- [x] I have run the [`pre-commit` checks](https://pre-commit.com/) with
`./isaaclab.sh --format`
- [x] I have made corresponding changes to the documentation
- [x] My changes generate no new warnings
- [ ] I have added tests that prove my fix is effective or that my
feature works
- [ ] I have updated the changelog and the corresponding version in the
extension's `config/extension.toml` file
- [ ] I have added my name to the `CONTRIBUTORS.md` or my name already
exists there

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Signed-off-by: Kelly Guo <kellyg@nvidia.com>