[intrinsics] Remove %_IsFunction inline intrinsic.

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 1977a5847d858f6acdbf2153acfdab926e668d70..be8d04c3ff0cfbe3da2f2e166d26569723553091 100644
--- a/src/compiler/js-intrinsic-lowering.h
+++ b/src/compiler/js-intrinsic-lowering.h
@@ -46,7 +46,6 @@ class JSIntrinsicLowering final : public AdvancedReducer {
   Reduction ReduceIncrementStatsCounter(Node* node);
   Reduction ReduceIsMinusZero(Node* node);
   Reduction ReduceIsInstanceType(Node* node, InstanceType instance_type);
-  Reduction ReduceIsFunction(Node* node);
   Reduction ReduceIsJSReceiver(Node* node);
   Reduction ReduceIsSmi(Node* node);
   Reduction ReduceJSValueGetValue(Node* node);