testing python version 3.9

Author: StigHaraldGustavsen

Diff for: .github/workflows/tests.yml

@@ -8,7 +8,7 @@ jobs:
     strategy:
       matrix:
         os: [ubuntu-latest]
-        python-version: ['3.10.9','3.11.0']
+        python-version: ['3.9.16','3.10.9']
     steps:
       - uses: actions/checkout@v3
         name: Set up Python ${{ matrix.python-version }}