[#31675] Remove last uses of JRequest in Joomla

Combined with #3677 this should remove all instances of JRequest from Joomla - which paves the way for it's removal in J4.0 :D

http://joomlacode.org/gf/project/joomla/tracker/?action=TrackerItemEdit&tracker_item_id=31675

Looking at the method signature of `getArray()` I think it doesn't work that way.
See http://api.joomla.org/cms-3/classes/JInput.html#method_getArray