doc: fix worker.resourceLimits type

PR-URL: #30664
Reviewed-By: Anna Henningsen <anna@addaleax.net>
Reviewed-By: Colin Ihrig <cjihrig@gmail.com>
Reviewed-By: Luigi Pinca <luigipinca@gmail.com>
Reviewed-By: Trivikram Kamat <trivikr.dev@gmail.com>

doc/api/worker_threads.md

@@ -162,7 +162,7 @@ When this function is used, no `'message'` event will be emitted and the
 added: REPLACEME
 -->
 
-* {Object|undefined}
+* {Object}
   * `maxYoungGenerationSizeMb` {number}
   * `maxOldGenerationSizeMb` {number}
   * `codeRangeSizeMb` {number}