Prefer websockets when providers support them (#13592)

Remove all flags and model settings.

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Co-authored-by: Codex <noreply@openai.com>

codex-rs/core/src/models_manager/model_info.rs

@@ -88,7 +88,6 @@ pub(crate) fn model_info_from_slug(slug: &str) -> ModelInfo {
         effective_context_window_percent: 95,
         experimental_supported_tools: Vec::new(),
         input_modalities: default_input_modalities(),
-        prefer_websockets: false,
         used_fallback_model_metadata: true, // this is the fallback model metadata
         supports_search_tool: false,
     }