fixed rsync command for frontent

nginx-mempool.conf has "root /var/www/mempool/browser;"

README.md

@@ -167,7 +167,7 @@ Install mempool dependencies from npm and build the frontend static HTML/CSS/JS:
 Install the output into nginx webroot folder:
 
 ```bash
-  sudo rsync -av --delete dist/mempool/ /var/www/html/
+  sudo rsync -av --delete dist/mempool /var/www/
 ```
 
 ## nginx + certbot