Change light themes default contrast from -0.08 to -0.06

[aganm]

I'm a light theme user and I felt like something was wrong with the light themes in godot. The issue was the negative contrast being a little bit too low, -0.08 overblows the highlights far too much. A small correction to -0.06 looks much better!

To save the time of other light theme users, I think it's a good idea to make that fix so that light themes look correct by default.

[Calinou]

Can you take screenshots to compare before/after in the editor?

[aganm]

For solarized light,

Here's a screenshot before (-0.08):

Screenshot after (-0.06):

[aganm]

For the regular Light, it's a more subtle difference, but still an improvement:

Screenshot before (-0.08):

Screenshot after (-0.06):

[aganm]

Oh, hmm.. I just noticed something. The light themes in godot 4 seem broken beyond what I initially thought.

At first, I only noticed the overblown highlights. But I went back to compare with godot 3 and the light themes in godot 3 are correct.

See the solarized light theme in godot 3 (default settings):

And in godot 4, the colors are overblown and the minimap has no highlight (default settings):

This PR somewhat fixes the overblown colors in godot 4, but the minimap highlight is still missing.

I double checked different godot 4 versions and the issue is present in all these versions:
4.0
4.1 beta 1
4.1 beta 2

[aganm]

Should I close this PR and open an issue instead?

[Calinou]

Should I close this PR and open an issue instead?

I think you can keep this PR open, but please open an issue for the minimap theming regression.

[akien-mga]

Thanks! And congrats for your first merged Godot contribution 🎉