geom manuals: Use ISO/IEC byte units

[ziaee]

Summary

The gpart manual says that sizes are specified in blocks, unless an SI
unit suffix is provided. This confuses new operators because GEOM uses
binary bytes, a large difference at modern storage pool sizes. Rewrite
suffixes in all GEOM manuals to consistently clarify this, matching what
we and the rest of the industry have been doing in other documentation.

MFC after: 3 days
Reported by: bbaovanc <[e-mail]>

[ziaee]

drop the IEC, it's technically an anachronism, and "binary byte sizes"
isn't any less clear.

[ziaee]

missed a spot, thanks bbaovanc!

[ziaee]

missed another spot

[ziaee]

use non-breaking spaces for unit sizes, unless we already use a hyphen on that page.

[fuz]

LGTM