LibJS: Remove m_first_invalid_property_range from ObjectExpression

This was state only used by the parser to output an error with
appropriate location. This shrinks the size of ObjectExpression from
120 bytes down to just 56. This saves roughly 2.5 MiB when loading
twitter.

Userland/Libraries/LibJS/Parser.h

@@ -282,6 +282,7 @@ private:
         ScopePusher* current_scope_pusher { nullptr };
 
         HashMap<StringView, Optional<Position>> labels_in_scope;
+        HashMap<size_t, Position> invalid_property_range_in_object_expression;
         HashTable<StringView>* referenced_private_names { nullptr };
 
         bool strict_mode { false };