testing/forgejo: security upgrade to 1.21.11-1

https://codeberg.org/forgejo/forgejo/src/branch/forgejo/RELEASE-NOTES.md#1-21-11-0

Security fixes:

• Fixed a privilege escalation through git push options that allows any user to change the visibility of any repository they can see, regardless of their level of access.
• Fixed a bug that allows user-supplied, non-sandboxed JavaScript to be run from the same domain as the forge, via /{owner}/{repo}/render/branch/{branch}/{filename} URLs.