ci: Fix FIPS jobs failing in forks of Gitaly

With 72497fc3 (ci: Add jobs which exercise Gitaly in FIPS mode, 2022-06-14), we have added a set of jobs which exercise Gitaly in FIPS mode. These jobs require a special runner that has booted into FIPS mode itself. Gitaly has been manually assigned such runners, but they are not generally available for any of Gitaly's forks. Consequentially, trying to run these jobs in any of our forks will eventually cause them to time out because no runner could be acquired. And because our first job rule for the FIPS jobs will automatically run when changes are merged to the default branch, this causes pipelines to fail in our forks.

Fix this issue by only automatically creating these jobs when run in the "official" repository. In case we're not running in that repository we'll instead just create these jobs with a manual trigger.