Staxrip: 2.1.8.5: System Theme Color destroys Dark Theme menus

[JJKylee]

Describe the bug

Setting Menu Style to System Theme Color destroys dark theme menus.
See these screenshots:

How to reproduce the issue

1. Go to Tools > Settings > User Interface.
2. Select any _dark theme_ and set Menu Style to System Theme Color.

Additional Notes and Suggestion

Since we already have a wide variety of themes, I believe _we don't need system theme color menu styles any more_.

[Dendraspis]

@stax76
Since a dark theme is the default, it might be okay to remove this setting. What do you think?

[stax76]

That feature don't appear important to me, I also think it's okay to remove it.

[Dendraspis]

And done.

I removed the whole related code and some old orphans.