update drone.yml

drone.yml

 
 - name: release
   image: plugins/gitea-release
-  depends_on:
-    - build
+  depends_on: [ build ]
+  when:
+    event: [ tag ]
   settings:
     title: release-linux-amd64
     note: CHANGELOG.md
     api_key:
       from_secret: gitea-release
     checksum: [ md5, sha1, sha256, sha512, adler32, crc32 ] 
+    file_exists: overwrite
     files:
       - src/radangel
       - src/contrib/websockify
       - radangel-release.tar.gz
-    file_exists: overwrite
-  when:
-    event: tag