Enable url preview in complement

[ShadowJonathan]

This is to soon add a removed test in matrix-org/complement#279, converted sytest "Test URL preview".

Might not play well with #14079

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.
  • Feel free to credit yourself, by adding a sentence "Contributed by @github_username." or "Contributed by [Your Name]." to the end of the entry.
• Pull request includes a sign off
• Code style is correct
  (run the linters)

Signed-off-by: Jonathan de Jong <jonathan@automatia.nl>

[clokep]

(I'm going to assume this can be merged since it has a green check and looks reasonable to me!)