doc: require node:process in assert doc examples

PR-URL: #53702
Reviewed-By: Benjamin Gruenbaum <[email protected]>
Reviewed-By: Chemi Atlow <[email protected]>
Reviewed-By: Ulises Gascón <[email protected]>

Author: mfdebian

doc/api/assert.md

@@ -269,6 +269,7 @@ process.on('exit', () => {
 
 ```cjs
 const assert = require('node:assert');
+const process = require('node:process');
 
 const tracker = new assert.CallTracker();