fix: remove redundant server file before deployment

.drone.yml

@@ -21,7 +21,6 @@ steps:
       - mkdir -p /opt/short-link/frontend
       # 拷贝编译产物
       - mv /opt/short-link/short-link-server /opt/short-link/short-link-server.bak
-      - rm /opt/short-link/short-link-server
       - cp backend/short-link-server /opt/short-link/short-link-server
       - cp -r frontend/dist/* /opt/short-link/frontend/
       - cp Caddyfile /root/projects/_conf/short-link.conf