doc: fix example of crypto.generateKeySync

doc: fix the example of crypto.generateKeySync

The "options" argument must be an object.

PR-URL: #40225
Reviewed-By: Qingyu Deng <i@ayase-lab.com>
Reviewed-By: Harshitha K P <harshitha014@gmail.com>
Reviewed-By: Tobias Nießen <tniessen@tnie.de>
Reviewed-By: Filip Skokan <panva.ip@gmail.com>

doc/api/crypto.md

@@ -3616,7 +3616,7 @@ const {
   generateKeySync
 } = await import('crypto');
 
-const key = generateKeySync('hmac', 64);
+const key = generateKeySync('hmac', { length: 64 });
 console.log(key.export().toString('hex'));  // e89..........41e
 ```
 
@@ -3625,7 +3625,7 @@ const {
   generateKeySync,
 } = require('crypto');
 
-const key = generateKeySync('hmac', 64);
+const key = generateKeySync('hmac', { length: 64 });
 console.log(key.export().toString('hex'));  // e89..........41e
 ```