Fix Python version matrix in CI workflow - quote version numbers to prevent YAML float conversion

Author: aledipa

.github/workflows/ci.yml

@@ -12,7 +12,7 @@ jobs:
 
     strategy:
       matrix:
-        python-version: [3.9, 3.10, 3.11]
+        python-version: ["3.9", "3.10", "3.11"]
 
     steps:
     - uses: actions/checkout@v4