zfs-program.8: fix orphan .Xr

Reported by:	phk
Reviewed by:	avg
MFC after:	2 weeks
Differential Revision:	https://reviews.freebsd.org/D24488

cddl/contrib/opensolaris/cmd/zfs/zfs-program.8

@@ -11,7 +11,7 @@
 .\" Copyright (c) 2016, 2017 by Delphix. All rights reserved.
 .\" Copyright (c) 2018 Datto Inc.
 .\"
-.Dd October 02, 2017
+.Dd April 18, 2020
 .Dt ZFS-PROGRAM 8
 .Os
 .Sh NAME
@@ -289,7 +289,7 @@ EBADF     EXDEV       EFBIG
 .Ss API Functions
 For detailed descriptions of the exact behavior of any zfs administrative
 operations, see the main
-.Xr zfs 1
+.Xr zfs 8
 manual page.
 .Bl -tag -width "xx"
 .It Em zfs.debug(msg)