Replace tests with python 3.9, using python 3.12 instead

.github/workflows/test.yml

@@ -17,7 +17,7 @@ jobs:
         # NOTE: qgis:stable points to the latest release, wheread qgis:latest points to qgis master
         QGIS_DOCKER_VERSION: ['qgis/qgis:ltr', 'qgis/qgis:stable']
         # NOTE: qgis uses its own python, but we want to check if there are problems interfacing with the engine while it uses different python versions
-        PYTHON_VERSION: ['3.9', '3.10', '3.11']
+        PYTHON_VERSION: ['3.10', '3.11', '3.12']
     runs-on: ${{ matrix.os }}
     env:
       GITHUB_DEF_BR: master