CI: remove Python 3.11 (does not work with detectron2)

Author: bertsky

.github/workflows/python-app.yml

@@ -20,7 +20,7 @@ jobs:
     runs-on: ubuntu-latest
     strategy:
       matrix:
-        python-version: ['3.8', '3.9', '3.10', '3.11']
+        python-version: ['3.8', '3.9', '3.10']
 
     steps:
     - uses: actions/checkout@v4