networking.vpnc: remove option

This PR is part of the networking.* namespace cleanup.

The Cisco VPN module is currently of limited value since it just creates
config files but does not manage services. The same functionality can be
achieved by using _environment.etc_ instead.

It would be a different situation if we had a full service module. So if
you are annoyed by this change, please consider write a more featureful
module and put its options unter _services.networking.vpnc_.

Note that this change removes options for *Cisco VPN*, not
*networkmanager-vpn*.

nixos/modules/rename.nix

@@ -235,6 +235,7 @@ with lib;
     (mkRemovedOptionModule [ "services" "zabbixServer" "dbPassword" ] "Use services.zabbixServer.database.passwordFile instead.")
     (mkRemovedOptionModule [ "systemd" "generator-packages" ] "Use systemd.packages instead.")
     (mkRemovedOptionModule [ "fonts" "enableCoreFonts" ] "Use fonts.fonts = [ pkgs.corefonts ]; instead.")
+    (mkRemovedOptionModule [ "networking" "vpnc" ] "Use environment.etc.\"vpnc/service.conf\" instead.")
 
     # ZSH
     (mkRenamedOptionModule [ "programs" "zsh" "enableSyntaxHighlighting" ] [ "programs" "zsh" "syntaxHighlighting" "enable" ])