Add more dast/vulnerability loose foreign keys to pipelines

These have been determined to be safe to swap for loose foreign keys in
https://gitlab.com/gitlab-org/gitlab/-/issues/348272 . We will start by
adding the loose foreign key and then we'll remove the foreign key in a
later MR.

lib/gitlab/database/gitlab_loose_foreign_keys.yml

+dast_site_profiles_pipelines:
+  - table: ci_pipelines
+    column: ci_pipeline_id
+    on_delete: async_delete
+vulnerability_feedback:
+  - table: ci_pipelines
+    column: pipeline_id
+    on_delete: async_nullify
 ci_pipeline_chat_data:
   - table: chat_names
     column: chat_name_id