doc: improve ECDH example

PR-URL: #22607
Reviewed-By: Rod Vagg <rod@vagg.org>
Reviewed-By: Colin Ihrig <cjihrig@gmail.com>
Reviewed-By: Ruben Bridgewater <ruben@bridgewater.de>
Reviewed-By: Luigi Pinca <luigipinca@gmail.com>

doc/api/crypto.md

@@ -703,9 +703,9 @@ If the `inputEncoding` is not provided, `key` is expected to be a [`Buffer`][],
 Example (uncompressing a key):
 
 ```js
-const { ECDH } = require('crypto');
+const { createECDH, ECDH } = require('crypto');
 
-const ecdh = ECDH('secp256k1');
+const ecdh = createECDH('secp256k1');
 ecdh.generateKeys();
 
 const compressedKey = ecdh.getPublicKey('hex', 'compressed');