fixing acl on kubeconfig

.gitlab/ci/build_docker_images.yml

@@ -46,6 +46,8 @@ cleanup_composer_image:
   needs: []
   variables:
     KEEP_N: 9   # Trim to the latest 9 revisions as the 10th will be deleted in the next stage
+  before_script:
+    - chmod go-r $KUBECONFIG
   script:
     - .gitlab/deployment_scripts/cleanup_revisions.sh