docs: fix manual page warnings

docs: fix manual page warnings

All warnings where about unnecessary quoting.  The scriptlet
below will tell what was wrong.

for I in ./top/top.1 ./ps/ps.1 ./*.[0-9]; do
    echo "== $I warnings =="
    man --warnings=all $I > /dev/null
done

This should probably be turned to 'make check' script.

Signed-off-by: Sami Kerola <kerolasa@iki.fi>