[turbofan] Move SimplifiedOperatorBuilder into JSGraph.

src/compiler/simplified-operator.h

Index: src/compiler/simplified-operator.h
diff --git a/src/compiler/simplified-operator.h b/src/compiler/simplified-operator.h
index 53b6b044a1ade8c1aa727e71f934bbc13f27d987..222679f9a6e0a828bc1a8c8a072b0d10500f3d2b 100644
--- a/src/compiler/simplified-operator.h
+++ b/src/compiler/simplified-operator.h
@@ -125,7 +125,7 @@ ElementAccess const& ElementAccessOf(const Operator* op) WARN_UNUSED_RESULT;
 //   - Bool: a tagged pointer to either the canonical JS #false or
 //           the canonical JS #true object
 //   - Bit: an untagged integer 0 or 1, but word-sized
-class SimplifiedOperatorBuilder final {
+class SimplifiedOperatorBuilder final : public ZoneObject {
  public:
   explicit SimplifiedOperatorBuilder(Zone* zone);