7956 "minimum" is misspelled in zpool manpage

illumos/illumos-gate@eba8726136851528470dad9bad27892859bc1e3e
https://github.com/illumos/illumos-gate/commit/eba8726136851528470dad9bad27892859bc1e3e

https://www.illumos.org/issues/7956

Reviewed by: Prashanth Sreenivasa <pks@delphix.com>
Reviewed by: Matthew Ahrens <mahrens@delphix.com>
Reviewed by: Sebastien Roy <sebastien.roy@delphix.com>
Reviewed by: Yuri Pankov <yuri.pankov@gmail.com>
Approved by: Richard Lowe <richlowe@richlowe.net>
Author: Brad Lewis <blewis@delphix.com>