programs/calls: enable dconf
programs/calls: enable dconf

GNOME Calls relies on dconf. Evidence supporting this claim:
https://packages.debian.org/sid/gnome-calls depends on
dconf-gsettings-backend.

Discussed in
https://github.com/NixOS/nixpkgs/pull/136537#issuecomment-1009903194 :

NixOS/nixpkgs,NixOS/nixpkgs,NixOS/nixpkgs,NixOS/nixpkgs,NixOS/nixpkgs,NixOS/nixpkgs,NixOS/nixpkgs,NixOS/nixpkgs,NixOS/nixpkgs,NixOS/nixpkgs,NixOS/nixpkgs,NixOS/nixpkgs,NixOS/nixpkgs,NixOS/nixpkgs,NixOS/nixpkgs