chore: update gtk4-output for the theme to set adwaita named colors

This is still a bit incomplete, and some apps use their own custom variables as well, for example the text editor.

cosmic-theme/src/output/mod.rs

@@ -1,8 +1,3 @@
-#[cfg(feature = "gtk4-theme")]
+#[cfg(feature = "gtk4-output")]
 /// Module for outputting the Cosmic gtk4 theme type as CSS
 pub mod gtk4_output;
-#[cfg(feature = "gtk4-theme")]
-pub use gtk4_output::*;
-
-#[cfg(feature = "ron-serialization")]
-pub use ron::*;