RFR: remove useless change from ifnode.cpp

[Aleksey Shipilev]

On 11/13/2018 03:21 PM, Roland Westrelin wrote:
> http://cr.openjdk.java.net/~roland/shenandoah/revert-ifnode-change/webrev.00/
> 
> MultiNode::proj_out() asserts the returned value is not null so the
> check in ifnode.cpp is dead code.

Looks good.

-Aleksey