Enable async GC for all

Fixes #569

workers/gcworker.py

@@ -15,7 +15,7 @@ class GarbageCollectionWorker(Worker):
   def _garbage_collection_repos(self):
     """ Performs garbage collection on repositories. """
     with UseThenDisconnect(app.config):
-      repository = find_repository_with_garbage(app.config.get('EXP_ASYNC_GARBAGE_COLLECTION', []))
+      repository = find_repository_with_garbage()
       if repository is None:
         logger.debug('No repository with garbage found')
         return