[TASK] Remove unused ViewHelpers from ext:belog

With the replacing of the DateTimePicker two ViewHelpers
became obsolete. Both are removed without substitution.

Resolves: #40189
Releases: master
Change-Id: Ic5b16875ed8213d693f54604d09faec53f98aca8
Reviewed-on: http://review.typo3.org/35603
Reviewed-by: Mathias Schreiber <mathias.schreiber@wmdb.de>
Tested-by: Mathias Schreiber <mathias.schreiber@wmdb.de>
Reviewed-by: Anja Leichsenring <aleichsenring@ab-softlab.de>
Tested-by: Anja Leichsenring <aleichsenring@ab-softlab.de>