chore: use gapic-generator-python 1.3.1 (#376)

* chore: use gapic-generator-python 1.3.1

PiperOrigin-RevId: 472772457

Source-Link: googleapis/googleapis@855b74d

Source-Link: https://github.com/googleapis/googleapis-gen/commit/b64b1e7da3e138f15ca361552ef0545e54891b4f
Copy-Tag: eyJwIjoiLmdpdGh1Yi8uT3dsQm90LnlhbWwiLCJoIjoiYjY0YjFlN2RhM2UxMzhmMTVjYTM2MTU1MmVmMDU0NWU1NDg5MWI0ZiJ9

* 🦉 Updates from OwlBot post-processor

See https://github.com/googleapis/repo-automation-bots/blob/main/packages/owl-bot/README.md

Co-authored-by: Owl Bot <gcf-owl-bot[bot]@users.noreply.github.com>

tests/unit/gapic/documentai_v1/test_document_processor_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 math

tests/unit/gapic/documentai_v1beta2/test_document_understanding_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 math

tests/unit/gapic/documentai_v1beta3/test_document_processor_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 math