doc: fix broken utf8 encoding

conversion to utf8 left some extra control character here,
remove it.

Signed-off-by: Oskar Schirmer <oskar@scara.com>
Cc: John Anthony Kazos Jr <jakj@j-a-k-j.com>
Cc: Rob Landley <rob@landley.net>
Signed-off-by: Jiri Kosina <jkosina@suse.cz>