[TASK] Remove backwards-compatibility below TYPO3 version 6.x

Remove check due to backwards-compatibility with $GLOBALS['TYPO3_VERSION'].

Resolves: #60525
Releases: 3.0
Change-Id: I148b9e354d25fcf6f3a540c70f84b7afb3fc400b
Reviewed-on: http://review.typo3.org/31760
Reviewed-by: Jochem de Groot <jochemdegroot@roquin.nl>
Tested-by: Jochem de Groot <jochemdegroot@roquin.nl>