theme: Remove unused staff parameter for listing themes (#20077)

This PR removes the `staff` parameter for listing themes, as it was not
used.

Release Notes:

- N/A

crates/languages/src/json.rs

@@ -3,7 +3,6 @@ use async_compression::futures::bufread::GzipDecoder;
 use async_tar::Archive;
 use async_trait::async_trait;
 use collections::HashMap;
-use feature_flags::FeatureFlagAppExt;
 use futures::StreamExt;
 use gpui::{AppContext, AsyncAppContext};
 use http_client::github::{latest_github_release, GitHubLspBinaryVersion};
@@ -77,13 +76,11 @@ impl JsonLspAdapter {
 
     fn get_workspace_config(language_names: Vec<String>, cx: &mut AppContext) -> Value {
         let action_names = cx.all_action_names();
-        let staff_mode = cx.is_staff();
 
         let font_names = &cx.text_system().all_font_names();
         let settings_schema = cx.global::<SettingsStore>().json_schema(
             &SettingsJsonSchemaParams {
                 language_names: &language_names,
-                staff_mode,
                 font_names,
             },
             cx,