[turbofan] Remove locally constructed simplified builders.

src/compiler/simplified-operator-reducer.cc

Index: src/compiler/simplified-operator-reducer.cc
diff --git a/src/compiler/simplified-operator-reducer.cc b/src/compiler/simplified-operator-reducer.cc
index a7f790563ebfe89672f7f16fe26a17dff4626e24..acd0f66ef65bf69b463853d398a7621bedf30227 100644
--- a/src/compiler/simplified-operator-reducer.cc
+++ b/src/compiler/simplified-operator-reducer.cc
@@ -15,7 +15,7 @@ namespace internal {
 namespace compiler {
 
 SimplifiedOperatorReducer::SimplifiedOperatorReducer(JSGraph* jsgraph)
-    : jsgraph_(jsgraph), simplified_(jsgraph->zone()) {}
+    : jsgraph_(jsgraph) {}
 
 
 SimplifiedOperatorReducer::~SimplifiedOperatorReducer() {}