man: remove the "Maintained by" references

man: remove the "Maintained by" references

At a glance through my system, around 2% of the man pages include such
statement.

Looking through git log, Jon has been active in a while and presumably
have moved on.

Most importantly the Copyright section isn't the best place to reference
the maintainer/contact person.

Signed-off-by: Emil Velikov <emil.l.velikov@gmail.com>
Signed-off-by: Lucas De Marchi <lucas.de.marchi@gmail.com>