fix test matrix

Author: snopoke

.github/workflows/tests.yml

@@ -12,8 +12,8 @@ jobs:
       max-parallel: 4
       matrix:
         python-version:
-          - 3.9
-          - 3.10
+          - "3.9"
+          - "3.10"
     steps:
       - uses: actions/checkout@v3
       - name: Set up Python ${{ matrix.python-version }}