Replace ZFS on Linux references with OpenZFS

This change updates the documentation to refer to the project
as OpenZFS instead ZFS on Linux.  Web links have been updated
to refer to https://github.com/openzfs/zfs.  The extraneous
zfsonlinux.org web links in the ZED and SPL sources have been
dropped.

Reviewed-by: George Melikov <mail@gmelikov.ru>
Reviewed-by: Richard Laager <rlaager@wiktel.com>
Reviewed-by: Ryan Moeller <ryan@iXsystems.com>
Signed-off-by: Brian Behlendorf <behlendorf1@llnl.gov>
Closes #11007

contrib/dracut/90zfs/module-setup.sh.in

@@ -41,7 +41,8 @@ install() {
 	dracut_install @bindir@/zgenhostid
 	dracut_install @sbindir@/zfs
 	dracut_install @sbindir@/zpool
-	# Workaround for zfsonlinux/zfs#4749 by ensuring libgcc_s.so(.1) is included
+	# Workaround for https://github.com/openzfs/zfs/issues/4749 by
+	# ensuring libgcc_s.so(.1) is included
 	if [[ -n "$(ldd @sbindir@/zpool | grep -F 'libgcc_s.so')" ]]; then
 		# Dracut will have already tracked and included it
 		:;