cups service: use cups.out everywhere

Seeing as the dev output is the default, we probably want cups.out
everywhere.

nixos/modules/services/printing/cupsd.nix

···
   bindir = pkgs.buildEnv {
     name = "cups-progs";
     paths =
-      [ cups additionalBackends cups_filters pkgs.ghostscript ]
+      [ cups.out additionalBackends cups_filters pkgs.ghostscript ]
       ++ optional cfg.gutenprint gutenprint
       ++ cfg.drivers;
     pathsToLink = [ "/lib/cups" "/share/cups" "/bin" ];
···
         description = "CUPS printing services";
       };
 
-    environment.systemPackages = [ cups ] ++ optional polkitEnabled cups-pk-helper;
+    environment.systemPackages = [ cups.out ] ++ optional polkitEnabled cups-pk-helper;
     environment.etc."cups".source = "/var/lib/cups";
 
-    services.dbus.packages = [ cups ] ++ optional polkitEnabled cups-pk-helper;
+    services.dbus.packages = [ cups.out ] ++ optional polkitEnabled cups-pk-helper;
 
     # Cups uses libusb to talk to printers, and does not use the
     # linux kernel driver. If the driver is not in a black list, it
···
         wants = [ "network.target" ];
         after = [ "network.target" ];
 
-        path = [ cups ];
+        path = [ cups.out ];
 
         preStart =
           ''