[turbofan] Remove unused BuildLoadGlobalProxy from AstGraphBuilder.

src/compiler/ast-graph-builder.cc

Index: src/compiler/ast-graph-builder.cc
diff --git a/src/compiler/ast-graph-builder.cc b/src/compiler/ast-graph-builder.cc
index fd395633e8a61767b414866414725103d29498c7..42869a75e7cb2f71e2e8ec95d54f5c4ae9c24aa8 100644
--- a/src/compiler/ast-graph-builder.cc
+++ b/src/compiler/ast-graph-builder.cc
@@ -3657,14 +3657,6 @@ Node* AstGraphBuilder::BuildLoadNativeContextField(int index) {
 }
 
 
-Node* AstGraphBuilder::BuildLoadGlobalProxy() {
-  Node* global = BuildLoadGlobalObject();
-  Node* proxy =
-      BuildLoadObjectField(global, JSGlobalObject::kGlobalProxyOffset);
-  return proxy;
-}
-
-
 Node* AstGraphBuilder::BuildLoadFeedbackVector() {
   if (!feedback_vector_.is_set()) {
     Node* closure = GetFunctionClosure();