[TASK] Remove obsolete require statements from ErrorHandler

As the autoloader is now always present through the bootstrap
and Composer class loader, the fallback of manually
requiring classes can be removed.

Resolves: #36061
Releases: master
Change-Id: I299232630a0390688bd683b64e5d31c422baa444
Reviewed-on: http://review.typo3.org/40759


Reviewed-by: Wouter Wolters <typo3@wouterwolters.nl>
Reviewed-by: Oliver Klee <typo3-coding@oliverklee.de>
Reviewed-by: Frederic Gaus <frederic.gaus@flagbit.de>
Tested-by: Wouter Wolters <typo3@wouterwolters.nl>
Reviewed-by: Christian Kuhn <lolli@schwarzbu.ch>
Tested-by: Christian Kuhn <lolli@schwarzbu.ch>