Missing in-place request-id checks in sbtc-registry on non-mainnet

[BowTiedRadone]

The sbtc-registry contract has a subtle issue in its complete-withdrawal-accept and complete-withdrawal-reject functions: neither includes a request-id check. While this isn’t a problem on mainnet — validate-protocol-caller ensures these functions are gated — it’s less clear on other networks. On non-mainnet environments, the contract deployer could influence the flow and allow a request-id greater than last-withdrawal-request-id.