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>

pgrep.1

@@ -218,10 +218,10 @@ and
 .B pgrep
 were introduced in Sun's Solaris 7.  This implementation is fully compatible.
 .SH AUTHOR
-.UR kjetilho\@ifi.uio.no
+.UR kjetilho@ifi.uio.no
 Kjetil Torgrim Homme
 .UE
 .SH "REPORTING BUGS"
 Please send bug reports to
-.UR procps\@freelists.org
+.UR procps@freelists.org
 .UE