(ci) Introduce tests:3.11 job (#194)

Set default PYTHON_VERSION to 3.11

.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
 
@@ -111,6 +111,9 @@ tests:3.10:
   variables:
     PYTHON_VERSION: "3.10"
 
+tests:3.11:
+  extends: .tests
+
 release:
   stage: release
   script: