chore: drop unsupported Python versions from CI

Remove Python 3.6 and 3.7 from the build matrix as they are no longer
supported (3.6 EOL: Dec 2021, 3.7 EOL: June 2023).

Current supported versions: 3.8, 3.9, 3.10, 3.11

🤖 Generated with [Claude Code](https://claude.com/claude-code)

Co-Authored-By: Claude <[email protected]>

Author: corneliusroemer

.github/workflows/build_and_publish.yml

@@ -54,7 +54,7 @@ jobs:
       fail-fast: false
       matrix:
         os: [ ubuntu-24.04, macOS-13 ]
-        python-version: [ 36, 37, 38, 39, 310, 311 ]
+        python-version: [ 38, 39, 310, 311 ]
 
     steps:
       - name: "Checkout code"