Remove obsolete comment

The sequence name is no longer stored in the sequence relation, since
1753b1b.

Author: petere

src/backend/commands/tablecmds.c

@@ -3140,12 +3140,6 @@ RenameRelation(RenameStmt *stmt)
 
 /*
  *		RenameRelationInternal - change the name of a relation
- *
- *		XXX - When renaming sequences, we don't bother to modify the
- *			  sequence name that is stored within the sequence itself
- *			  (this would cause problems with MVCC). In the future,
- *			  the sequence name should probably be removed from the
- *			  sequence, AFAIK there's no need for it to be there.
  */
 void
 RenameRelationInternal(Oid myrelid, const char *newrelname, bool is_internal)