Fixes gitlab_schema for Ci::Builds

This custom model is clobbering gitlab_schema for the ci_builds table,
causing false failures for cross-db query detection

This now causes other specs to fail because we now have the correct
schema for ci_builds, so allowlist those specs.

db/migrate/20210629031900_associate_existing_dast_builds_with_variables.rb

@@ -20,6 +20,7 @@ class AssociateExistingDastBuildsWithVariables < ActiveRecord::Migration[6.1]
   class Build < ApplicationRecord
     self.table_name = 'ci_builds'
     self.inheritance_column = :_type_disabled
+    self.gitlab_schema = :gitlab_ci
 
     default_scope { where(name: :dast, stage: :dast) } # rubocop:disable Cop/DefaultScope
   end

spec/support/database/cross-join-allowlist.yml

@@ -64,7 +64,6 @@
 - "./spec/mailers/emails/pipelines_spec.rb"
 - "./spec/migrations/20210907211557_finalize_ci_builds_bigint_conversion_spec.rb"
 - "./spec/migrations/cleanup_legacy_artifact_migration_spec.rb"
-- "./spec/migrations/migrate_protected_attribute_to_pending_builds_spec.rb"
 - "./spec/migrations/re_schedule_latest_pipeline_id_population_with_all_security_related_artifact_types_spec.rb"
 - "./spec/migrations/schedule_migrate_security_scans_spec.rb"
 - "./spec/models/ci/build_spec.rb"
@@ -118,3 +117,8 @@
 - "./spec/support/shared_examples/requests/graphql_shared_examples.rb"
 - "./spec/support/shared_examples/services/packages_shared_examples.rb"
 - "./spec/support/shared_examples/workers/idempotency_shared_examples.rb"
+- "./spec/migrations/associate_existing_dast_builds_with_variables_spec.rb"
+- "./spec/migrations/schedule_pages_metadata_migration_spec.rb"
+- "./spec/migrations/schedule_copy_ci_builds_columns_to_security_scans2_spec.rb"
+- "./spec/lib/gitlab/background_migration/copy_ci_builds_columns_to_security_scans_spec.rb"
+- "./spec/lib/gitlab/background_migration/migrate_pages_metadata_spec.rb"