Try python 3.9 in pipeline matrix.

Author: joshuabmoore

.github/workflows/run_unit_tests.yaml

@@ -8,7 +8,7 @@ jobs:
     runs-on: ubuntu-latest
     strategy:
       matrix:
-        python-version: ["3.8"]
+        python-version: ["3.8", "3.9"]
     steps:
       - uses: actions/checkout@v3
       - name: Setup python ${{ matrix.python-version }}