Update obsolete comment

table_tuple_update's update_indexes argument hasn't been a boolean since
commit 19d8e2308bc5.

Backpatch-through: 16
(cherry picked from commit f4ec7154ce8d3e3a572baea682c1f58890a72589)

Author: alvherre

src/include/access/tableam.h

@@ -1520,8 +1520,8 @@ table_tuple_delete(Relation rel, ItemPointer tid, CommandId cid,
  * Output parameters:
  *	tmfd - filled in failure cases (see below)
  *	lockmode - filled with lock mode acquired on tuple
- *  update_indexes - in success cases this is set to true if new index entries
- *		are required for this tuple
+ *	update_indexes - in success cases this is set if new index entries
+ *		are required for this tuple; see TU_UpdateIndexes
  *
  * Normal, successful return value is TM_Ok, which means we did actually
  * update it.  Failure return codes are TM_SelfModified, TM_Updated, and