[FOLLOWUP][FEATURE] JavaScript-based icon API

Fix the AJAX route name in the Icons.js module.

Resolves: #70583
Releases: master
Change-Id: I1ce12aecc8aeac13e6d29af0b424ba2614f97504
Reviewed-on: http://review.typo3.org/44074


Reviewed-by: Georg Ringer <georg.ringer@gmail.com>
Tested-by: Georg Ringer <georg.ringer@gmail.com>
Reviewed-by: Anja Leichsenring <aleichsenring@ab-softlab.de>
Tested-by: Anja Leichsenring <aleichsenring@ab-softlab.de>