ada: Fix small oversight in removal of N_Unchecked_Expression node

In addition to Resolve_Indexed_Component, Eval_Indexed_Component can also
set the Do_Range_Check flag on the expressions of an N_Indexed_Component
node through the call on Check_Non_Static_Context, so this also needs to
be blocked by the Kill_Range_Check flag.

gcc/ada/ChangeLog:

	* sem_eval.adb (Eval_Indexed_Component): Clear Do_Range_Check on
	the expressions if Kill_Range_Check is set on the node.