www/mhonarc: update 2.6.18 -> 2.6.24, switch to other upstream source

• the sympa community maintains this code this patch switches to this source and update to last version

PR: 252466
Submitted by: geoffroy desvernay <dgeo@centrale-marseille.fr>
Approved by: kerndtr@kerndt.com (maintainer timeout)
Relnotes: https://github.com/sympa-community/MHonArc/blob/master/CHANGES