doc: remove superfluous URL require statement

Since v10.0.0, the `URL` class is available on the global object, so
using a `require` statement to access it is no longer necessary.

Author: MarkTiedemann

doc/api/url.md

@@ -132,8 +132,6 @@ and a `base` is provided, it is advised to validate that the `origin` of
 the `URL` object is what is expected.
 
 ```js
-const { URL } = require('url');
-
 let myURL = new URL('http://anotherExample.org/', 'https://example.org/');
 // http://anotherexample.org/