hg: shenandoah/jdk11: [backport] Revert "Handle missing ShenandoahWriteBarrierRB case"

[ashipile at redhat.com]

Changeset: 29b7a8916e68
Author:    shade
Date:      2018-08-02 16:11 +0200
URL:       http://hg.openjdk.java.net/shenandoah/jdk11/rev/29b7a8916e68

[backport] Revert "Handle missing ShenandoahWriteBarrierRB case"

! src/hotspot/share/gc/shenandoah/c2/shenandoahSupport.cpp