Revert "Remove cx from ThemeSettings (#38836)" (#39691)

This reverts commit a2a7bd139a.

This caused themes to not load correctly on startup, you needed to edit
your settings.

Release Notes:

- N/A

crates/language/src/language_settings.rs

@@ -500,7 +500,7 @@ fn merge_with_editorconfig(settings: &mut LanguageSettings, cfg: &EditorconfigPr
 }
 
 impl settings::Settings for AllLanguageSettings {
-    fn from_settings(content: &settings::SettingsContent) -> Self {
+    fn from_settings(content: &settings::SettingsContent, _cx: &mut App) -> Self {
         let all_languages = &content.project.all_languages;
 
         fn load_from_content(settings: LanguageSettingsContent) -> LanguageSettings {