revert(rfq): remove confirmed trade broadcasts

[cesarenaldi]

Summary

• revert py-sdk PR feat(rfq): support confirmed trade broadcasts #104 while the backend RFQ_TRADE broadcast is not deployed
• remove RFQ_TRADE parsing, RfqTradeEvent exports, and integration coverage

Verification

• uv run ruff format --check && uv run ruff check
• uv run pyright
• uv run pytest tests/integration/test_rfq.py started but did not complete because live API key derivation was rate limited with HTTP 429 after 10 tests passed

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Note

Low Risk
Narrow API removal aligned with undeployed backend behavior; no changes to quote, confirm, or execution-update flows.

Overview
Reverts RFQ confirmed trade websocket support until the backend RFQ_TRADE broadcast is deployed.

The public RfqTradeEvent type and its export from polymarket / polymarket.rfq are removed, and RfqEvent again only covers quote requests, confirmation requests, and execution updates. The quoter session no longer handles RFQ_TRADE messages or _parse_trade.

Integration tests drop the dedicated trade-broadcast case and the happy-path flow stops after RFQ_EXECUTION_UPDATE instead of also expecting a trade event.

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