[BUGFIX] Wrong class in t3lib_TCEforms_Suggest

Due to an backport error from #21588 a wrong class was introduced with. This
patch replaces the wrong class with the correct one so suggest wizard is
working again.

Change-Id: I9059452b2ceb9952ce6426a90872fee1b225c3b6
Resolves: #48052
Releases: 4.7, 4.5
Reviewed-on: https://review.typo3.org/20694
Reviewed-by: Wouter Wolters
Tested-by: Wouter Wolters