openbgpd: replace cvengler as openbgpd maintainer

Discussed with kloenk in a private chat.  See also #509060.

pkgs/by-name/op/openbgpd/package.nix

@@ -60,7 +60,7 @@ stdenv.mkDerivation rec {
     description = "Free implementation of the Border Gateway Protocol, Version 4. It allows ordinary machines to be used as routers exchanging routes with other systems speaking the BGP protocol";
     license = lib.licenses.isc;
     homepage = "http://www.openbgpd.org/";
-    maintainers = with lib.maintainers; [ kloenk ];
+    maintainers = with lib.maintainers; [ cvengler ];
     platforms = lib.platforms.linux;
   };
 }