[BUGFIX] Remove RemoveXSS credit link

The current link to RemoveXSS project is broken and
no new one can be found. The patch removes the link
from about module but keeps other references in the
source files

Change-Id: Iff9590aae3cd093c17553a94d1d5c88afde54834
Releases: master, 6.2
Resolves: #65485
Reviewed-on: http://review.typo3.org/37534


Reviewed-by: Wouter Wolters <typo3@wouterwolters.nl>
Tested-by: Wouter Wolters <typo3@wouterwolters.nl>