Fix use of ActiveRecord::Base in RepositoryCheck

Relates to https://gitlab.com/gitlab-org/gitlab/-/issues/350651

.rubocop_todo/database/multiple_databases.yml

@@ -25,7 +25,6 @@ Database/MultipleDatabases:
   - lib/gitlab/import_export/group/relation_tree_restorer.rb
   - lib/gitlab/legacy_github_import/importer.rb
   - lib/gitlab/seeder.rb
-  - lib/system_check/orphans/repository_check.rb
   - spec/db/schema_spec.rb
   - spec/initializers/database_config_spec.rb
   - spec/lib/backup/manager_spec.rb

lib/system_check/orphans/repository_check.rb

@@ -57,8 +57,8 @@ module SystemCheck
           WHERE (p.repository_storage LIKE ?)
         "
 
-        query = ActiveRecord::Base.send(:sanitize_sql_array, [sql, storage_name]) # rubocop:disable GitlabSecurity/PublicSend
-        ActiveRecord::Base.connection.select_all(query).rows.try(:flatten!) || []
+        query = ::Project.sanitize_sql_array([sql, storage_name])
+        ::Project.connection.select_all(query).rows.try(:flatten!) || []
       end
 
       def fetch_disk_namespaces(storage_path)