Remove unnessessary full qualified class names.
Cleanup docheaders.

Resolves: #57878
Releases: 6.3
Change-Id: I5bcdb80c27da1698fd1446a001907d83c6845507
Reviewed-on: https://review.typo3.org/29444
Reviewed-by: Anja Leichsenring
Tested-by: Anja Leichsenring
Reviewed-by: Wouter Wolters
Tested-by: Wouter Wolters