Remove more references to 'model' in GPUI APIs (#23693)

Release Notes:

- N/A

crates/language_model_selector/src/language_model_selector.rs

@@ -33,7 +33,7 @@ impl LanguageModelSelector {
 
         let all_models = Self::all_models(cx);
         let delegate = LanguageModelPickerDelegate {
-            language_model_selector: cx.model().downgrade(),
+            language_model_selector: cx.entity().downgrade(),
             on_model_changed: on_model_changed.clone(),
             all_models: all_models.clone(),
             filtered_models: all_models,