8299845: Remove obsolete comments in DirtyCardToOopClosure::get_actual_top

Co-authored-by: Y. Srinivas Ramakrishna <ysr@openjdk.org>
Reviewed-by: tschatzl, sjohanss

src/hotspot/share/gc/shared/space.cpp

@@ -58,10 +58,6 @@ HeapWord* DirtyCardToOopClosure::get_actual_top(HeapWord* top,
         // Otherwise, it is possible that the object starting on the dirty
         // card spans the entire card, and that the store happened on a
         // later card.  Figure out where the object ends.
-        // Use the block_size() method of the space over which
-        // the iteration is being done.  That space (e.g. CMS) may have
-        // specific requirements on object sizes which will
-        // be reflected in the block_size() method.
         top = top_obj + cast_to_oop(top_obj)->size();
       }
     } else {