[DOC] Update documentation because cObject RECORDS don't provides "if" directly

See http://docs.typo3.org/typo3cms/TyposcriptReference/ContentObjects/Records/Index.html

Change-Id: I50a672a5a4c0c392613496732ea14e6283ebadcd
Reviewed-on: https://review.typo3.org/27927
Reviewed-by: Georg Ringer
Tested-by: Georg Ringer