fix: make manager reject messages for already completed sigs

[ChaoticTempest]

Noticed this wasn't handled quite yet. This would be the case where a node's indexer is behind but slowly catches up and tries to do signature request, but it has already been completed for other nodes

[github-actions]

Terraform Feature Environment Destroy (dev-773)

Terraform Initialization ⚙️success

Terraform Destroy success

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No changes. No objects need to be destroyed.

Either you have not created any objects yet or the existing objects were
already deleted outside of Terraform.

Destroy complete! Resources: 0 destroyed.

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