Fix zpool(8) list example to match actual format

Fix zpool(8) list example to match actual format

a05dfd00 (Illumos 5147) has swapped FRAG and EXPANDSZ,
so it's natural to modify these examples.

 # zpool list | head -1
 NAME     SIZE  ALLOC   FREE  EXPANDSZ   FRAG    CAP  DEDUP  HEALTH  ALTROOT
                              ^^^^^^^^^^^^^^^

Reviewed-by: Giuseppe Di Natale <dinatale2@llnl.gov>
Reviewed-by: Brian Behlendorf <behlendorf1@llnl.gov>
Signed-off-by: Tomohiro Kusumi <kusumi.tomohiro@osnexus.com>
Closes #7244