[!!!][BUGFIX] Intermediate fix for Toolbar problems

Removes the hasDropDown() method of the ToolbarItemInterface

Resolves: #62929
Releases: master
Change-Id: I758e43b0874712c0a6e9e08b2b5c22f189573d6f
Reviewed-on: http://review.typo3.org/34191
Reviewed-by: Markus Klein <klein.t3@reelworx.at>
Tested-by: Markus Klein <klein.t3@reelworx.at>