Fix bogus comment that claimed that the new BACKUP METHOD line in

backup_label was new in 9.0. Spotted by Fujii Masao.

src/backend/access/transam/xlog.c

@@ -9826,9 +9826,9 @@ read_backup_label(XLogRecPtr *checkPointLoc, bool *backupEndRequired)
 				(errcode(ERRCODE_OBJECT_NOT_IN_PREREQUISITE_STATE),
 				 errmsg("invalid data in file \"%s\"", BACKUP_LABEL_FILE)));
 	/*
-	 * BACKUP METHOD line is new in 9.0. Don't complain if it doesn't exist,
-	 * in case you're restoring from a backup taken with an 9.0 beta version
-	 * that didn't emit it.
+	 * BACKUP METHOD line is new in 9.2. We can't restore from an older backup
+	 * anyway, but since the information on it is not strictly required, don't
+	 * error out if it's missing for some reason.
 	 */
 	if (fscanf(lfp, "BACKUP METHOD: %19s", backuptype) == 1)
 	{