Error responses documented on portfolio history endpoint

Broker API

The Get Account Portfolio History operation now documents its error responses. Behavior is unchanged.

• Adds documented 401, 403, 404, 422, 429, 500, and 504 responses.
• Adds a PortfolioHistoryError response schema, titled "Portfolio History Error" so it no longer collides with the existing Error schema.
• Documents the Deprecated-Params response header.

Affected Endpoints

• GET /v1/trading/accounts/{account_id}/account/portfolio/history