Run gems specs in maintenance pipelines

The following discussion from !125859 (merged) should be addressed:

• @splattael started a discussion: (+2 comments)

  It seems that the scheduled pipeline https://gitlab.com/gitlab-org/gitlab/-/pipelines/928848137 failed to run gem related pipelines:

  

This was originally done by !125859 (merged) but reverted by !126194 (merged) because some workflow rules were preventing the gem pipelines from being created: