Onboard tests/packit to staging Fedora CI

Signed-off-by: Nikola Forró <nforro@redhat.com>

Author: nforro

secrets/packit/stg/packit-service.yaml.j2

@@ -154,6 +154,7 @@ enabled_projects_for_fedora_ci:
   - https://src.fedoraproject.org/rpms/python-scikit-build-core
   - https://src.fedoraproject.org/rpms/python-specfile
   - https://src.fedoraproject.org/rpms/spglib
+  - https://src.fedoraproject.org/tests/packit
 
 # Log Detective interface server URL and token
 logdetective_enabled: false