Fix reference figure tests on Windows

[JeroenDelcour]

Reference figure tests are failing, presumably because the ANSI escape characters for colors will be different on Windows.

I guess there will have to be a separate set of reference figures for Windows.

[JeroenDelcour]

On second thought, Windows tests are only to make sure that Colorama works. It makes little sense to duplicate their tests. In any case, since Colorama replaces ANSI escape characters with win32 codes, which AFAIK can't be written as text to a file, so testing automatically reference figures with color would be impossible on Windows anyway.

Better to not do testing on Windows at all.