man page: updated bug tracker link

doc/libmicrohttpd.3

@@ -43,4 +43,4 @@ You can obtain the latest version from
 .Lk https://www.gnu.org/software/libmicrohttpd/ Ns .
 .Sh BUGS
 Report bugs by using
-.Lk https://gnunet.org/bugs/ "Mantis" Ns .
+.Lk https://bugs.gnunet.org/set_project.php?project_id=10 "Mantis" Ns .