doc: fix casing in util.markPromiseAsHandled section

Signed-off-by: Antoine du Hamel <duhamelantoine1995@gmail.com>
PR-URL: #66206
Reviewed-By: Luigi Pinca <luigipinca@gmail.com>
Reviewed-By: James M Snell <jasnell@gmail.com>

Author: aduh95

doc/api/util.md

@@ -1904,7 +1904,7 @@ equality.
 added: v26.10.0
 -->
 
-* `promise` {promise} The promise to mark as handled
+* `promise` {Promise} The promise to mark as handled
 
 Marks a promise as handled so that unhandled rejections are ignored and are not
 reported to the `'unhandledrejection'` event.