[turbofan] Remove the TryLowerDirectJSCall hack from generic lowering.

src/compiler/js-generic-lowering.h

Index: src/compiler/js-generic-lowering.h
diff --git a/src/compiler/js-generic-lowering.h b/src/compiler/js-generic-lowering.h
index 89467dbdd2cdeef8629f8911789dbbdcee2f573c..9811ba8451810ecceea2ed392b0b536cf6d5c5c2 100644
--- a/src/compiler/js-generic-lowering.h
+++ b/src/compiler/js-generic-lowering.h
@@ -41,9 +41,6 @@ class JSGenericLowering final : public Reducer {
   void ReplaceWithBuiltinCall(Node* node, Builtins::JavaScript id, int args);
   void ReplaceWithRuntimeCall(Node* node, Runtime::FunctionId f, int args = -1);
 
-  // Helper for optimization of JSCallFunction.
-  bool TryLowerDirectJSCall(Node* node);
-
   Zone* zone() const;
   Isolate* isolate() const;
   JSGraph* jsgraph() const { return jsgraph_; }