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/exec/src/lib.rs

@@ -374,7 +374,7 @@ pub async fn run_main(cli: Cli, codex_linux_sandbox_exe: Option<PathBuf>) -> any
     ));
     let default_model = thread_manager
         .get_models_manager()
-        .get_default_model(&config.model, &config, RefreshStrategy::OnlineIfUncached)
+        .get_default_model(&config.model, RefreshStrategy::OnlineIfUncached)
         .await;
 
     // Handle resume subcommand by resolving a rollout path and using explicit resume API.