docs(core): remove contextual-user note from developer fragments module

Drop the cross-module explanatory comment from the developer fragment file to keep this module focused on developer-envelope update fragments.

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

Author: charley-oai

codex-rs/core/src/context_manager/updates/developer_update_fragments.rs

@@ -26,11 +26,6 @@ use codex_protocol::protocol::TurnContextItem;
 // ---------------------------------------------------------------------------
 // Settings-update fragments for the developer envelope
 // ---------------------------------------------------------------------------
-//
-// Contextual-user settings-update fragments are assembled in `updates.rs`
-// (currently `EnvironmentContext::diff_from_turn_context_item(...)`) and the
-// corresponding fragment types live in their own modules (for example
-// `environment_context.rs` and `instructions/contextual_user_fragments.rs`).
 
 struct PermissionsUpdateFragment {
     text: String,