Improve docs about video support

[emilk]

We do support AV1 on native, and now the docs say so too.

• Closes Update video docs, now that we have native AV1 video support #7662

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• I have read and agree to Contributor Guide and the Code of Conduct
• I've included a screenshot or gif (if applicable)
• I have tested the web demo (if applicable):
  • Using examples from latest main build: rerun.io/viewer
  • Using full set of examples from nightly build: rerun.io/viewer
• The PR title and labels are set such as to maximize their usefulness for the next release's CHANGELOG
• If applicable, add a new check to the release checklist!
• If have noted any breaking changes to the log API in CHANGELOG.md and the migration guide
• I've read the docs preview at https://landing-e6yens1hp-rerun.vercel.app/docs/reference/video

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Deployed docs

Commit	Link
64d4f24	https://landing-8v0rzf8vn-rerun.vercel.app/docs