Suppress 'signal process started' message when nginx config is restored (related to issue #4995) (#6747)

acme.sh

@@ -3524,7 +3524,7 @@ _restoreNginx() {
   done
 
   _info "Reloading nginx"
-  if ! nginx -s reload >/dev/null; then
+  if ! nginx -s reload >/dev/null 2>&1; then
     _err "An error occurred while reloading nginx, please open an issue on $PROJECT."
     return 1
   fi