fix: missing import

Author: rpenido

openedx/core/djangoapps/content_libraries/signal_handlers.py

@@ -21,7 +21,7 @@
 
 from lms.djangoapps.grades.api import signals as grades_signals
 
-from .api import library_collection_locator, library_component_usage_key
+from .api import library_collection_locator, library_component_usage_key, library_container_locator
 from .models import ContentLibrary, LtiGradedResource
 
 log = logging.getLogger(__name__)