Deorbit catman. The tradeoff of disk for performance has long since tipped
in favor of just rendering the manpage instead of relying on pre-formatted
catpages. Note, this does not impede the ability to use existing catpages,
it just removes the utility to generate them.

Reviewed by: imp, allanjude
Approved by: emaste (mentor)
Differential Revision: https://reviews.freebsd.org/D12317