i-t: don't suggest zpool-import with altroot to /root

This *will fail* when remounted by the real root

Reviewed-by: Brian Behlendorf <behlendorf1@llnl.gov>
Signed-off-by: Ahelenia Ziemiańska <nabijaczleweli@nabijaczleweli.xyz>
Closes openzfs#12148

contrib/initramfs/scripts/zfs

@@ -875,7 +875,7 @@ mountroot()
 		echo ""
 		echo "No pool imported. Manually import the root pool"
 		echo "at the command prompt and then exit."
-		echo "Hint: Try:  zpool import -R ${rootmnt} -N ${ZFS_RPOOL}"
+		echo "Hint: Try:  zpool import -N ${ZFS_RPOOL}"
 		shell
 	fi