dhcpcd: Don't depend on network-interfaces.target

Dhcpcd automatically detects new interfaces, so we can start it right
away.

modules/services/networking/dhcpcd.nix

@@ -94,8 +94,7 @@ in
     boot.systemd.services.dhcpcd =
       { description = "DHCP Client";
 
-        wantedBy = [ "multi-user.target" ];
-        after = [ "network-interfaces.target" ];
+        wantedBy = [ "network.target" ];
 
         path = [ dhcpcd pkgs.nettools pkgs.openresolv ];