Update .gitlab-ci.yml file

.gitlab-ci.yml

@@ -2,6 +2,8 @@ before_script:
   - docker login -u "$CI_REGISTRY_USER" -p "$CI_REGISTRY_PASSWORD" $CI_REGISTRY
 
 build-master:
+  tags:
+    - maven
   script:
     - docker build --pull -t $CI_REGISTRY_IMAGE/maven .
     - docker push $CI_REGISTRY_IMAGE/maven