benchmark: removed unused arguments from callbacks

Removed unused arguments 'buf' and 'rinfo' from the callbacks.

PR-URL: #14919
Reviewed-By: Rich Trott <rtrott@gmail.com>
Reviewed-By: James M Snell <jasnell@gmail.com>
Reviewed-By: Tobias Nießen <tniessen@tnie.de>
Reviewed-By: Luigi Pinca <luigipinca@gmail.com>
Reviewed-By: Ruben Bridgewater <ruben@bridgewater.de>

Author: abhishek-raj

benchmark/dgram/multi-buffer.js

@@ -64,7 +64,7 @@ function server() {
     }, dur * 1000);
   });
 
-  socket.on('message', function(buf, rinfo) {
+  socket.on('message', function() {
     received++;
   });
 

benchmark/dgram/offset-length.js

@@ -56,7 +56,7 @@ function server() {
     }, dur * 1000);
   });
 
-  socket.on('message', function(buf, rinfo) {
+  socket.on('message', function() {
     received++;
   });
 

benchmark/dgram/single-buffer.js

@@ -56,7 +56,7 @@ function server() {
     }, dur * 1000);
   });
 
-  socket.on('message', function(buf, rinfo) {
+  socket.on('message', function() {
     received++;
   });