[BUGFIX] Load date-time picker in scheduler module

The date-time picker must be loaded explicitly.

Fix for regression #31027 that was introduced to 4.5 with
issue #33629

Change-Id: I06014d1a3ed9ce6584272632f1532ba1bcf92843
Fixes: #31027
Related: #33629
Releases: 4.5
Reviewed-on: https://review.typo3.org/17765
Reviewed-by: Christian Kuhn
Tested-by: Christian Kuhn