MFC r321023:

The ctladm man page incorrectly duplicated the text for the
delete subcommand in the modify section. Rewrite the
modify description text in two places to say modify/modified
instead of remove/removed.

PR: 220710
Submitted by: sseekamp@risei.net
Reviewed by: mav@
Differential Revision: https://reviews.freebsd.org/D11608