Allow RTMP sources for RTSPtoWeb

[trvrnrth]

Proposed change

The recommended RTSPtoWeb (rtsp-to-web addon) supports RTMP sources so we now allow use of the WebRTC provider for RTMP sources.

Type of change

• Dependency upgrade
• Bugfix (non-breaking change which fixes an issue)
• New integration (thank you!)
• New feature (which adds functionality to an existing integration)
• Breaking change (fix/feature causing existing functionality to break)
• Code quality improvements to existing code or addition of tests

Additional information

• This PR fixes or closes issue: fixes #
• This PR is related to issue: FFMPEG to WebRTC blakeblackshear/frigate#1824
• Link to documentation pull request:

Checklist

• The code change is tested and works locally.
• Local tests pass. Your PR cannot be merged unless tests pass
• There is no commented out code in this PR.
• I have followed the development checklist
• The code has been formatted using Black (black --fast homeassistant tests)
• Tests have been added to verify that the new code works.

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• Documentation added/updated for www.home-assistant.io

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• The manifest file has all fields filled out correctly.
  Updated and included derived files by running: python3 -m script.hassfest.
• New or updated dependencies have been added to requirements_all.txt.
  Updated by running python3 -m script.gen_requirements_all.
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[probot-home-assistant]

Hey there @home-assistant/core, mind taking a look at this pull request as it has been labeled with an integration (camera) you are listed as a code owner for? Thanks!
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[allenporter]

I've updated the PR description to remove the mention of the add-on since I think this is kind of out of scope of the responsibility of home assistant core. I think there are already many significant caveats mentioned in the docs about limitations and differences between the two services RTSPtoWeb and RTSPtoWebRTC that it's not necessarily worth flagging.

[allenporter]

Thank you very much for this change 👍🏼

(Can merge once CI passes)