nixos: services: servarr: fix 'enableAll' logic

I renamed the option and refactored how it worked to make it more
explicit that it enables the entire suite by default, with explicit
opt-out of individual components (or fine-grained opt-in as an
alternative).

hosts/nixos/porthos/services.nix

@@ -144,7 +144,7 @@ in
     sabnzbd.enable = true;
     # The whole *arr software suite
     servarr = {
-      enable = true;
+      enableAll = true;
       # ... But not Lidarr because I don't care for music that much
       lidarr = {
         enable = false;