Remove final mention of FREEZE_PAGE from comments

b7493e1ab3 removed leftover mentions of XLOG_HEAP2_FREEZE_PAGE records
from comments but neglected to remove one mention of FREEZE_PAGE.

Reported off-list by Alexander Lakhin

src/backend/access/transam/clog.c

@@ -984,8 +984,8 @@ ExtendCLOG(TransactionId newestXact)
 /*
  * Remove all CLOG segments before the one holding the passed transaction ID
  *
- * Before removing any CLOG data, we must flush XLOG to disk, to ensure
- * that any recently-emitted FREEZE_PAGE records have reached disk; otherwise
+ * Before removing any CLOG data, we must flush XLOG to disk, to ensure that
+ * any recently-emitted records with freeze plans have reached disk; otherwise
  * a crash and restart might leave us with some unfrozen tuples referencing
  * removed CLOG data.  We choose to emit a special TRUNCATE XLOG record too.
  * Replaying the deletion from XLOG is not critical, since the files could