ART: Fix bug in DCE not removing phis from catch phi uses

Due to the missing edges between throwing instructions and catch phis
DCE needs to manually remove dead instructions from catch phi users,
being overly conservative if the inputs are not in the dead blocks.
DCE used to do this for normal instructions, but it needs to do the
same for phis.

Change-Id: I7edfcb84ec6ff7303945d5d5cd436b1d1e95df2a