chore(deps): update dependency setuptools to v60.9.1 (googleapis#1207)

* chore(deps): update dependency setuptools to v60.9.1

* serialize showcase mtls tests

Co-authored-by: Anthonios Partheniou <partheniou@google.com>

Author: renovate-bot

.github/workflows/tests.yaml

@@ -83,6 +83,7 @@ jobs:
     strategy:
       matrix:
         target: [showcase_mtls, showcase_mtls_alternative_templates]
+      max-parallel: 1
     runs-on: ubuntu-latest
     steps:
       - uses: actions/checkout@v2

requirements.txt

@@ -7,4 +7,4 @@ protobuf==3.19.4
 pypandoc==1.7.2
 PyYAML==6.0
 dataclasses==0.6  # TODO(busunkim) remove when 3.6 support is dropped
-setuptools==60.9.0
+setuptools==60.9.1