Update GitHub action for uploading package to PyPi

Bump setup-python from v1 to v2

.github/workflows/pythonpublish.yml

@@ -10,7 +10,7 @@ jobs:
     steps:
     - uses: actions/checkout@v2
     - name: Set up Python
-      uses: actions/setup-python@v1
+      uses: actions/setup-python@v2
       with:
         python-version: '3.x'
     - name: Install dependencies