python3Packages.wxPython_4_1: propagate six

```
[...]
  File "/nix/store/mmwa03ack302jfzhd98bqycimhji9s2m-python3.10-wxPython-4.1.1/lib/python3.10/site-packages/wx/lib/embeddedimage.py", line 18, in <module>
    from six import BytesIO
ModuleNotFoundError: No module named 'six'
```

pkgs/development/python-modules/wxPython/4.1.nix

@@ -13,6 +13,7 @@
 , wxGTK
 , pillow
 , numpy
+, six
 , libXinerama
 , libSM
 , libXxf86vm
@@ -70,7 +71,11 @@ buildPythonPackage rec {
     webkitgtk
   ];
 
-  propagatedBuildInputs = [ pillow numpy ];
+  propagatedBuildInputs = [
+    pillow
+    numpy
+    six
+  ];
 
   DOXYGEN = "${doxygen}/bin/doxygen";