Fix warning when using textMateThemeFromScheme from lib-contrib

[mateusauler]

When using the textMateThemeFromScheme function from lib-contrib, a warning is generated:

trace: Obsolete option `colorScheme.colors' is used. It was renamed to `colorScheme.palette'.

This PR fixes this issue.

[jkuball]

I'd also be very interested in getting this merged. It is really a no-brainer. Thanks for the PR! Hopefully the maintainer finds some time in the future for this :)

As a small workaround, you could just monkeypatch the deprecation warning. That's what I am doing now for bat:

programs.bat.themes."ghetto-stylix".src = textMateThemeFromScheme {
  scheme = config.colorScheme // {colors = config.colorScheme.palette;};
};