black no longer supports python 3.9, and now fails only in 3.9 environments

removing style checks from github actions under 3.9, though not yet
entirely deprecating 3.9

psf/black#4842

Author: agentmorris

.github/workflows/python_style_checks.yml

@@ -12,7 +12,7 @@ jobs:
       fail-fast: false
       matrix:
         os: [ubuntu-latest]
-        python-version: ['3.9', '3.10', '3.11', '3.12']
+        python-version: ['3.10', '3.11', '3.12']
     steps:
       - name: Checkout repository
         uses: actions/checkout@v4