[ci] #166: Fixup to use newest syntax

The tools jobs were not triggered by the MR based pipelines

.gitlab-ci.yml

@@ -11,8 +11,8 @@ variables:
 image: $DOCKER_IMAGE/$PYTHON_VERSION:latest
 
 .code_changes:
-  only:
-    changes:
+  rules:
+    - changes:
       - duniterpy/**/*.py
       - tests/**/*.py
       - examples/*.py