Update supported python versions

Author: vyahello

.github/workflows/assess-code.yml

@@ -7,9 +7,9 @@ jobs:
       max-parallel: 4
       matrix:
         python-version:
-          - 3.6
           - 3.7
           - 3.8
+          - 3.9
     steps:
     - uses: actions/checkout@v1
     - name: Set up Python ${{ matrix.python-version }}