[turbofan] Drop the obsolete TypeGuard operator.

src/compiler/js-intrinsic-lowering.h

Index: src/compiler/js-intrinsic-lowering.h
diff --git a/src/compiler/js-intrinsic-lowering.h b/src/compiler/js-intrinsic-lowering.h
index f4b869561245e3d66f928fe06a312ebc75840ec8..5c7bd5eb53e591a5bd2ea56b8c621ae23341ce14 100644
--- a/src/compiler/js-intrinsic-lowering.h
+++ b/src/compiler/js-intrinsic-lowering.h
@@ -39,8 +39,6 @@ class JSIntrinsicLowering final : public AdvancedReducer {
  private:
   Reduction ReduceCreateIterResultObject(Node* node);
   Reduction ReduceDeoptimizeNow(Node* node);
-  Reduction ReduceDoubleHi(Node* node);
-  Reduction ReduceDoubleLo(Node* node);
   Reduction ReduceGeneratorClose(Node* node);
   Reduction ReduceGeneratorGetInputOrDebugPos(Node* node);
   Reduction ReduceGeneratorGetResumeMode(Node* node);