contract: remove clean_payloads() and check pending request before decrement counter

[ppca]

Part of addressing the audit about request counter. We should not need clean_payloads() anymore because the yield/resume will always either time out (a couple hundred blocks) or return signature, either way it will remove the request from pending_requests, so no request will be left in pending forever.

[github-actions]

Terraform Feature Environment Destroy (dev-697)

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Pusher: @ChaoticTempest, Action: pull_request, Working Directory: ``, Workflow: Terraform Feature Env (Destroy)