CI: bump Python versions

Author: mgeier

.github/workflows/version-matrix.yml

@@ -35,13 +35,12 @@ jobs:
               SPHINX_PACKAGE: "sphinx==7.1.2"
 
           # a few Python versions using latest Sphinx release
-          - env:
-              PYTHON_VERSION: "3.8"
           - env:
               PYTHON_VERSION: "3.10"
           - env:
-              PYTHON_VERSION: "3.13-dev"
-              PYTHONWARNINGS: default
+              PYTHON_VERSION: "3.11"
+          - env:
+              PYTHON_VERSION: "3.13"
 
     env: ${{ matrix.env || fromJSON('{}') }}
     steps: