Fix typo: dasboard -> dashboard (#3416)

cmd/frps/root.go

@@ -76,7 +76,7 @@ func init() {
 	rootCmd.PersistentFlags().IntVarP(&vhostHTTPPort, "vhost_http_port", "", 0, "vhost http port")
 	rootCmd.PersistentFlags().IntVarP(&vhostHTTPSPort, "vhost_https_port", "", 0, "vhost https port")
 	rootCmd.PersistentFlags().Int64VarP(&vhostHTTPTimeout, "vhost_http_timeout", "", 60, "vhost http response header timeout")
-	rootCmd.PersistentFlags().StringVarP(&dashboardAddr, "dashboard_addr", "", "0.0.0.0", "dasboard address")
+	rootCmd.PersistentFlags().StringVarP(&dashboardAddr, "dashboard_addr", "", "0.0.0.0", "dashboard address")
 	rootCmd.PersistentFlags().IntVarP(&dashboardPort, "dashboard_port", "", 0, "dashboard port")
 	rootCmd.PersistentFlags().StringVarP(&dashboardUser, "dashboard_user", "", "admin", "dashboard user")
 	rootCmd.PersistentFlags().StringVarP(&dashboardPwd, "dashboard_pwd", "", "admin", "dashboard password")