Account deactivation: Add info on leaving rooms

[fadenb]

Deactivating an account - in addition to the already listed things - also makes the user leave all rooms they are in.

Pull Request Checklist

• Pull request is based on the develop branch
• Pull request includes a changelog file. The entry should:
  • Be a short description of your change which makes sense to users. "Fixed a bug that prevented receiving messages from other servers." instead of "Moved X method from EventStore to EventWorkerStore.".
  • Use markdown where necessary, mostly for code blocks.
  • End with either a period (.) or an exclamation mark (!).
  • Start with a capital letter.
• Pull request includes a sign off
• Code style is correct (run the linters)

Signed-off-by: FadenB [email protected]

[dklimpel]

This information is also already part of #8932

[clokep]

This would need develop merged into to fix the build.

This information is also already part of #8932

I see no reason to not improve the docs before that's landed! 👍

[clokep]

It seems that #8932 was merged in the meantime so I'm going to close this. Thanks for your contribution!