[ci] feat: improve readability on gitlab run rules

.gitlab/deployment.yaml

@@ -7,11 +7,10 @@ deployment:
     name: "cr.simoncor.net/siempie/ansible-deployment:latest"
     entrypoint: ["/bin/sh", "-c"]
   rules:
-    - if: '$CI_PIPELINE_SOURCE == "push"'
-    - if: '$CI_PIPELINE_SOURCE == "merge_request_event"'
-    - if: '$CI_COMMIT_BRANCH == $CI_DEFAULT_BRANCH'
-    - when: "never"
 
+    # run only on push to default branch
+    - if: '$CI_PIPELINE_SOURCE == "push" && $CI_COMMIT_BRANCH == $CI_DEFAULT_BRANCH'
+    - when: "never"
 
   # prepare ssh
   before_script:
@@ -25,7 +24,6 @@ deployment:
         echo "$SSH_DEPLOYMENT_KEY" > ~/.ssh/id_ed25519
         chmod 600 ~/.ssh/id_ed25519
 
-
   # deployment commands
   script: