Revert "[core] add optional status_code to error events (#6865)" (#6955)

This reverts commit c2ec477d93.

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codex-rs/protocol/src/protocol.rs

@@ -686,8 +686,6 @@ pub struct ExitedReviewModeEvent {
 #[derive(Debug, Clone, Deserialize, Serialize, JsonSchema, TS)]
 pub struct ErrorEvent {
     pub message: String,
-    #[serde(default)]
-    pub http_status_code: Option<u16>,
 }
 
 #[derive(Debug, Clone, Deserialize, Serialize, JsonSchema, TS)]
@@ -1365,8 +1363,6 @@ pub struct UndoCompletedEvent {
 #[derive(Debug, Clone, Deserialize, Serialize, JsonSchema, TS)]
 pub struct StreamErrorEvent {
     pub message: String,
-    #[serde(default)]
-    pub http_status_code: Option<u16>,
 }
 
 #[derive(Debug, Clone, Deserialize, Serialize, JsonSchema, TS)]