[BUGFIX] WorkspaceMenu still depends on prototype

A small regression was found when switching
from prototype to jQuery.
The String.startWith method which was
added by prototype.js does not exist anymore.

This does not allow to reload module+pagetree
anymore.

Releases: master
Resolves: #62989
Change-Id: I74fdfc8b648f2bf7912ff4ea58b0a158836e3d9e
Reviewed-on: http://review.typo3.org/34211
Reviewed-by: Anja Leichsenring <aleichsenring@ab-softlab.de>
Tested-by: Anja Leichsenring <aleichsenring@ab-softlab.de>
Reviewed-by: Oliver Hader <oliver.hader@typo3.org>
Tested-by: Oliver Hader <oliver.hader@typo3.org>