[BUGFIX] No margin below context menus (in page tree)

Resolves: #53684
Releases: 6.2
Change-Id: I3be203934a724822ea8990f7b3ca04135521982c
Reviewed-on: https://review.typo3.org/25453
Reviewed-by: Jost Baron
Tested-by: Jost Baron
Reviewed-by: Ernesto Baschny
Tested-by: Ernesto Baschny