fix: revert issue rendering for `<a>` element (#7171)
- Issue title rendering can lead to nested `<a>` which is incorrect. So
revert a portion of forgejo/forgejo#6715.
- Integration test adjusted
- Resolves forgejo/forgejo#7076
Reviewed-on: https://codeberg.org/forgejo/forgejo/pulls/7171
Reviewed-by: 0ko <0ko@noreply.codeberg.org>
Co-authored-by: Gusted <postmaster@gusted.xyz>
Co-committed-by: Gusted <postmaster@gusted.xyz>