Disable NetworkManager-wait-online system service

This service is presumably useful for devices that need to ensure there
is an active internet connection before starting other systemd units.
This is neither the case for end-user devices as the an active internet
connection is only needed after login nor the case for server-like
systems as they normally have a static / dhcp-based network configuration
which does not require switchable network configuration profiles.

modules/core/networking.nix

@@ -23,6 +23,9 @@ in
     };
   };
   config = {
+    # disable NetworkManager-wait-online by default
+    systemd.services.NetworkManager-wait-online.enable = lib.mkDefault false;
+
     networking.networkmanager = {
       # Enable networkmanager. REMEMBER to add yourself to group in order to use nm related stuff.
       enable = true;