chore: rm remote models fflag (#11699)

rm `remote_models` feature flag.

We see issues like #11527 when a user has `remote_models` disabled, as
we always use the default fallback `ModelInfo`. This causes issues with
model performance.

Builds on #11690, which helps by warning the user when they are using
the default fallback. This PR will make that happen much less frequently
as an accidental consequence of disabling `remote_models`.

codex-rs/core/src/thread_manager.rs

@@ -230,12 +230,11 @@ impl ThreadManager {
 
     pub async fn list_models(
         &self,
-        config: &Config,
         refresh_strategy: crate::models_manager::manager::RefreshStrategy,
     ) -> Vec<ModelPreset> {
         self.state
             .models_manager
-            .list_models(config, refresh_strategy)
+            .list_models(refresh_strategy)
             .await
     }