Change Python versions in CI to reflect new GH Actions environment

Author: alessiostalla

.github/workflows/pythonapp.yml

@@ -6,7 +6,7 @@ jobs:
   build:
     strategy:
       matrix:
-        python: [ 3.8', '3.9', '3.10', '3.11', '3.12' ]
+        python: [ '3.8', '3.9', '3.10', '3.11', '3.12', '3.13' ]
     runs-on: ubuntu-latest
     steps:
       - uses: actions/checkout@v4