nixos/wpa_supplicant: don't log that wpa_supplicant.conf is ignored with allowAuxiliaryImperativeNetworks = true

The warning is wrong with `allowAuxiliaryImperativeNetworks`[1] being
set to `true` because both files are included in this case with `-c` and
`-I`.

[1] https://nixos.org/manual/nixos/stable/options.html#opt-networking.wireless.allowAuxiliaryImperativeNetworks

nixos/modules/services/networking/wpa_supplicant.nix

@@ -114,7 +114,7 @@ let
 
       script =
       ''
-        ${optionalString configIsGenerated ''
+        ${optionalString (configIsGenerated && !cfg.allowAuxiliaryImperativeNetworks) ''
           if [ -f /etc/wpa_supplicant.conf ]; then
             echo >&2 "<3>/etc/wpa_supplicant.conf present but ignored. Generated ${configFile} is used instead."
           fi