8253392: remove PhaseCCP_DCE declaration

remove the deprecated declaration PhaseCCP_DCE

Reviewed-by: neliasso, phh

Author: Xin Liu

src/hotspot/share/opto/compile.hpp

@@ -69,7 +69,6 @@ class PhaseGVN;
 class PhaseIterGVN;
 class PhaseRegAlloc;
 class PhaseCCP;
-class PhaseCCP_DCE;
 class PhaseOutput;
 class RootNode;
 class relocInfo;