chore: remove hardcoded maintainer for google-cloud-bigquery-storage (#16082)

I created #16081
to follow up on ensuring that teams have permissions to maintain to
handwritten libraries

Author: parthea

.github/CODEOWNERS

@@ -3,5 +3,3 @@
 
 # Default owner for all directories not owned by others
 *                                             @googleapis/cloud-sdk-python-team @googleapis/cloud-sdk-librarian-team
-
-/packages/google-cloud-bigquery-storage/      @googleapis/bigquery-team @googleapis/cloud-sdk-librarian-team