Update CI matrix to only include currently supported Python versions

Author: Bryan Bartley

.github/workflows/python-app.yml

@@ -12,7 +12,7 @@ jobs:
       matrix:
         # Default builds are on Ubuntu
         os: [ubuntu-latest]
-        python-version: ['3.7', '3.8', '3.9', '3.10']
+        python-version: ['3.9', '3.10', '3.11', '3.12', '3.13']
         include:
           # Also test on macOS and Windows using latest Python 3
           - os: macos-latest