clarify comment in example nginx config

docs/example.nginx.conf

@@ -2,7 +2,7 @@
 #   to work with CryptPad. This example WILL NOT WORK AS IS. For best results,
 #   compare the sections of this configuration file against a working CryptPad
 #   installation (http server by the Nodejs process). If you are using CryptPad
-#   in production, contact sales@cryptpad.fr
+#   in production and require professional support please contact sales@cryptpad.fr
 
 server {
     listen 443 ssl http2;