[ci] Define extends on a one-liner

.gitlab-ci.yml

@@ -28,36 +28,31 @@ image: $DOCKER_IMAGE/$PYTHON_VERSION:latest
       - pyproject.toml
 
 format:
-  extends:
-    - .code_changes
+  extends: .code_changes
   stage: checks
   script:
     - black --check duniterpy tests examples
 
 build:
-  extends:
-    - .changes
+  extends: .changes
   stage: checks
   script:
     - poetry build
 
 isort:
-  extends:
-    - .code_changes
+  extends: .code_changes
   stage: checks
   script:
     - isort --check duniterpy tests examples
 
 type:
-  extends:
-    - .code_changes
+  extends: .code_changes
   stage: checks
   script:
     - mypy duniterpy tests examples --ignore-missing-imports
 
 lint:
-  extends:
-    - .code_changes
+  extends: .code_changes
   stage: checks
   tags: [redshift]
   script: