doc: update parameter type for fsPromises.chmod()

This was overlooked in #31085.

PR-URL: #31115
Reviewed-By: Ruben Bridgewater <ruben@bridgewater.de>
Reviewed-By: Rich Trott <rtrott@gmail.com>
Reviewed-By: David Carlier <devnexen@gmail.com>
Reviewed-By: Luigi Pinca <luigipinca@gmail.com>

Author: cjihrig

doc/api/fs.md

@@ -4654,7 +4654,7 @@ added: v10.0.0
 -->
 
 * `path` {string|Buffer|URL}
-* `mode` {integer}
+* `mode` {string|integer}
 * Returns: {Promise}
 
 Changes the permissions of a file then resolves the `Promise` with no