Remove more dead code after Object.observe removal

src/isolate-inl.h

Index: src/isolate-inl.h
diff --git a/src/isolate-inl.h b/src/isolate-inl.h
index c27b7a700d4143aee6afd0a10a69cb205296252c..214117879caee97253befe8e8fe90130fa6d76c2 100644
--- a/src/isolate-inl.h
+++ b/src/isolate-inl.h
@@ -73,7 +73,11 @@ bool Isolate::is_catchable_by_javascript(Object* exception) {
 
 
 Handle<JSGlobalObject> Isolate::global_object() {
-  return Handle<JSGlobalObject>(context()->global_object(), this);
+  return handle(context()->global_object(), this);
+}
+
+Handle<JSObject> Isolate::global_proxy() {
+  return handle(context()->global_proxy(), this);
 }