[archives] fix URL of Renater's archives

fc-discuss/archives-header.md

@@ -7,5 +7,4 @@ title: Archives of the old Frama-C-discuss mailing list
 
 This page gathers the archives of the old Frama-C-discuss archives, that was hosted by [Inria](https://www.inria.fr)'s gforge before its demise at the
 end of 2020. To search for mails newer than September 2020, please visit
-the page of the new mailing list on [Renater](https://groupes.renater.fr/frama-c-discuss)
-
+the page of the new mailing list on [Renater](https://groupes.renater.fr/sympa/arc/frama-c-discuss)