Fix python version to 3.8.12

- update to `actions/setup-python@v2`

Author: charlielewisme

.github/workflows/publish-to-pypi.yml

@@ -12,7 +12,7 @@ jobs:
     steps:
       - uses: actions/checkout@master
       - name: Set up Python 3.8.12
-        uses: actions/setup-python@v1
+        uses: actions/setup-python@v2
         with:
           python-version: "3.8.12"
       - name: Build a binary wheel and a source tarball