RFR(T): 8216482: Shenandoah: typo in ShenandoahBarrierSetC2::clone_barrier_at_expansion() causes failed compilations

[Roland Westrelin]

Thanks for the review, Tobias. Oracle doesn't build Shenandoah, right?
so I can push that straight to jdk 12, no need to go through the submit
repo?

Roland.