Update .gitlab-ci.yml

.gitlab-ci.yml

@@ -52,6 +52,8 @@ build-jar:
 deploy-to-maven:
   stage: deploy
   script: ./gradlew -i uploadArchives -Pmaven_pass=$MAVEN_PASS
+  only:
+    - master
   cache:
     key: "$CI_COMMIT_REF_NAME"
     policy: push