fix errant always-on log message regarding 'setup'

Author: shellscape

lib/Server.js

@@ -343,9 +343,10 @@ function Server(compiler, options) {
     },
 
     setup: () => {
-      log('Using "setup" is deprecated and will be removed in the next major version. Please use the "before" and "after" hooks instead.');
-      log('If "setup" was working fine for you until now, simply replace it with "before"');
-      if (typeof options.setup === 'function') { options.setup(app, this); }
+      if (typeof options.setup === 'function') {
+        log('The `setup` option is deprecated and will be removed in v3. Please update your config to use `before`');
+        options.setup(app, this);
+      }
     }
   };