CI: remove Python 3.11 from test matrix

Author: dmgav

.github/workflows/testing.yml

@@ -17,7 +17,7 @@ jobs:
     strategy:
       matrix:
         host-os: ["ubuntu-latest", "macos-latest", "windows-latest"]
-        python-version: ["3.11", "3.12", "3.13"]
+        python-version: ["3.12", "3.13"]
         numpy-version: ["2.4.0"]
         pyqt-version: ["5.15"]
         include: