Simplify check and remove outdated comment.

R=bmeurer@chromium.org
BUG=

Review URL: https://codereview.chromium.org/1496263002

Cr-Commit-Position: refs/heads/master@{#32604}

src/objects-inl.h

@@ -5323,8 +5323,7 @@ bool Code::IsWeakObjectInOptimizedCode(Object* object) {
   } else if (object->IsPropertyCell()) {
     object = PropertyCell::cast(object)->value();
   }
-  if (object->IsJSObject() || object->IsJSProxy()) {
-    // JSProxy is handled like JSObject because it can morph into one.
+  if (object->IsJSReceiver()) {
     return FLAG_weak_embedded_objects_in_optimized_code;
   }
   if (object->IsFixedArray()) {