(ci) Set default PYTHON_VERSION to 3.11 (#442)

Moved pre-commit and git installation from 3.9 to 3.11 container

.gitlab-ci.yml

@@ -6,7 +6,7 @@ stages:
 
 variables:
   DOCKER_IMAGE: "registry.duniter.org/docker/python3/poetry"
-  PYTHON_VERSION: "3.9"
+  PYTHON_VERSION: "3.11"
 
 image: $DOCKER_IMAGE/$PYTHON_VERSION:latest
 
@@ -121,6 +121,8 @@ tests:3.8:
 
 tests:3.9:
   extends: .tests
+  variables:
+    PYTHON_VERSION: "3.9"
 
 tests:3.10:
   extends: .tests
@@ -129,8 +131,6 @@ tests:3.10:
 
 tests:3.11:cov:
   extends: .tests
-  variables:
-    PYTHON_VERSION: "3.11"
   coverage: '/(?i)total.*\s+(\d+%)/'
   script:
     - poetry install