Disable pipelines on default branch for non canonical projects

See merge request https://gitlab.com/gitlab-org/gitlab/-/merge_requests/134832



Merged-by: Lin Jen-Shin <jen-shin@gitlab.com>
Approved-by: Lin Jen-Shin <jen-shin@gitlab.com>
Reviewed-by: Niklas <mc.taucher2003@gmail.com>
Reviewed-by: Lin Jen-Shin <jen-shin@gitlab.com>
Reviewed-by: Nao Hashizume <nhashizume@gitlab.com>
Co-authored-by: Niklas <mc.taucher2003@gmail.com>
Co-authored-by: Nao Hashizume <nhashizume@gitlab.com>