remove unused ignore

Author: jrmccluskey

sdks/python/apache_beam/ml/rag/ingestion/spanner_it_test.py

@@ -41,7 +41,7 @@
 try:
   from testcontainers.core.container import DockerContainer
 except ImportError:
-  DockerContainer = None  # type: ignore[assignment]
+  DockerContainer = None
 # pylint: enable=wrong-import-order, wrong-import-position