doc: simplify process.memoryUsage() example code

Using util.inspect doesn't change the output in this case

PR-URL: https://github.com/nodejs/node/pull/9560
Reviewed-By: Myles Borins <myles.borins@gmail.com>
Reviewed-By: Rich Trott <rtrott@gmail.com>
Reviewed-By: Roman Reiss <me@silverwind.io>
Reviewed-By: Colin Ihrig <cjihrig@gmail.com>
Reviewed-By: Anna Henningsen <anna@addaleax.net>

doc/api/process.md

@@ -768,9 +768,7 @@ Returns an object describing the memory usage of the Node.js process
 measured in bytes.
 
 ```js
-const util = require('util');
-
-console.log(util.inspect(process.memoryUsage()));
+console.log(process.memoryUsage());
 ```
 
 This will generate: