chore: upgrade gapic-generator-python to 0.39.1 (#64)

feat(v2beta3, v2beta2): introducing fields: ListQueuesRequest.read_mask, GetQueueRequest.read_mask, Queue.task_ttl, Queue.tombstone_ttl, Queue.stats and introducing messages: QueueStats
feat: add from_service_account_info method to clients
docs(v2beta3): updates to max burst size description
docs(v2beta2): updates to AppEngineHttpRequest description
test: add 3.9 unit tests
docs: fix type references in docstrings

cloud-tasks/snippets/noxfile.py

@@ -85,7 +85,7 @@ def get_pytest_env_vars() -> Dict[str, str]:
 
 # DO NOT EDIT - automatically generated.
 # All versions used to tested samples.
-ALL_VERSIONS = ["2.7", "3.6", "3.7", "3.8"]
+ALL_VERSIONS = ["2.7", "3.6", "3.7", "3.8", "3.9"]
 
 # Any default versions that should be ignored.
 IGNORED_VERSIONS = TEST_CONFIG['ignored_versions']