Add loose foreign key ci_pipeline_schedules.owner_id

We will remove the foreign key in a later MR but for now we can start
with adding the LFK.

lib/gitlab/database/gitlab_loose_foreign_keys.yml

@@ -79,6 +79,10 @@ project_pages_metadata:
   - table: ci_job_artifacts
     column: artifacts_archive_id
     on_delete: async_nullify
+ci_pipeline_schedules:
+  - table: users
+    column: owner_id
+    on_delete: async_nullify
 ci_group_variables:
   - table: namespaces
     column: group_id