Remove FK dast_scanner_profiles_builds.ci_build_id as we have LFK

In https://gitlab.com/gitlab-org/gitlab/-/merge_requests/77908 we
already added a ["loose foreign key"](
https://docs.gitlab.com/ee/development/database/loose_foreign_keys.html)
to replace this foreign key. Now that this has been running fine in
production we should be OK to remove the foreign key altogether.

This was added in a post-deployment migration as we want to ensure that
they have the correct code running with the loose foreign key in place
before we remove the foreign key to ensure that there isn't any lost
deletes.

Changelog: other

db/post_migrate/20220110224913_remove_dast_scanner_profiles_builds_ci_build_id_fk.rb

+# frozen_string_literal: true
+
+class RemoveDastScannerProfilesBuildsCiBuildIdFk < Gitlab::Database::Migration[1.0]
+  disable_ddl_transaction!
+
+  CONSTRAINT_NAME = 'fk_e4c49200f8'
+
+  def up
+    with_lock_retries do
+      remove_foreign_key_if_exists(:dast_scanner_profiles_builds, :ci_builds, name: CONSTRAINT_NAME)
+    end
+  end
+
+  def down
+    add_concurrent_foreign_key(:dast_scanner_profiles_builds, :ci_builds, column: :ci_build_id, on_delete: :cascade, name: CONSTRAINT_NAME)
+  end
+end

db/schema_migrations/20220110224913

+d8b206e26f6dd7e9d5f2b2d8cc5ce2e2bbe2d8d33317948f8cf110fe41872a5d
\ No newline at end of file

db/structure.sql

@@ -29817,9 +29817,6 @@ ALTER TABLE ONLY gitlab_subscriptions
 ALTER TABLE ONLY ci_triggers
     ADD CONSTRAINT fk_e3e63f966e FOREIGN KEY (project_id) REFERENCES projects(id) ON DELETE CASCADE;
 
-ALTER TABLE ONLY dast_scanner_profiles_builds
-    ADD CONSTRAINT fk_e4c49200f8 FOREIGN KEY (ci_build_id) REFERENCES ci_builds(id) ON DELETE CASCADE;
-
 ALTER TABLE ONLY merge_requests
     ADD CONSTRAINT fk_e719a85f8a FOREIGN KEY (author_id) REFERENCES users(id) ON DELETE SET NULL;