chore: use gapic-generator-python 1.3.1 (#40)

- [ ] Regenerate this pull request now.

PiperOrigin-RevId: 472772457

Source-Link: googleapis/googleapis@855b74d

Source-Link: googleapis/googleapis-gen@b64b1e7
Copy-Tag: eyJwIjoiLmdpdGh1Yi8uT3dsQm90LnlhbWwiLCJoIjoiYjY0YjFlN2RhM2UxMzhmMTVjYTM2MTU1MmVmMDU0NWU1NDg5MWI0ZiJ9

Author: gcf-owl-bot[bot]

packages/google-cloud-bigquery-data-exchange/tests/unit/gapic/bigquery_data_exchange_v1beta1/test_analytics_hub_service.py

@@ -18,8 +18,8 @@
 # try/except added for compatibility with python < 3.8
 try:
     from unittest import mock
-    from unittest.mock import AsyncMock
-except ImportError:
+    from unittest.mock import AsyncMock  # pragma: NO COVER
+except ImportError:  # pragma: NO COVER
     import mock
 
 import grpc