add quotes due to yaml strangeness

.github/workflows/coverage.yml

@@ -11,14 +11,13 @@ jobs:
     runs-on: ubuntu-latest
     strategy:
       matrix:
-        python-version: [3.8, 3.9, 3.10, 3.11, 3.12]
+        python-version: ["3.8", "3.9", "3.10", "3.11", "3.12"]
     steps:
     - uses: actions/checkout@master
     - uses: pdm-project/setup-pdm@v4
       name: Install PDM
       with:
         python-version: ${{ matrix.python-version }}
-        cache: true
     - name: Generate coverage report
       run: |
         pdm install