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/vim/src/vim.rs

@@ -1913,7 +1913,7 @@ impl From<settings::ModeContent> for Mode {
 }
 
 impl Settings for VimSettings {
-    fn from_settings(content: &settings::SettingsContent) -> Self {
+    fn from_settings(content: &settings::SettingsContent, _cx: &mut App) -> Self {
         let vim = content.vim.clone().unwrap();
         Self {
             default_mode: vim.default_mode.unwrap().into(),