Destroying `fastly_ngwaf_workspace_signal` error / possible race-condition

[ejthurgo]

When destroying a fastly_ngwaf_workspace_signal resource.
It seems the terraform provider destroys the referencing rule, but then is unable to delete the signal due to the rule still referencing it?

[21:14:34] module.fastly_ngwaf_all_requests_visibility[0].fastly_ngwaf_workspace_rule.all_requests: Destruction complete after 2s
[21:14:34] ╷
[21:14:34] │ Error: 400 - Bad Request:
[21:14:34] │
[21:14:34] │ Title: The request is not valid
[21:14:34] │ Detail: Could not delete signal: it is currently being used by a rule