mark search keys sensitive

[buckelij]

This sets the Search Service primary_key and secondary_key values as sensitive so they are redacted from console output. Additionally, this marks the Question Answering custom_question_answering_search_service_key key as sensitive - this key will likely often be set from the primary_key of a terraform-managed Search Service and so it would be redacted, but I think it makes sense to mark the field Sensitive explicitly.

[stephybun]

Thanks for this @buckelij CI was failing because the files weren't formatted - this is fixed by running make fmt I hope you don't mind I went ahead and did that for you. Otherwise LGTM 👍

[github-actions]

This functionality has been released in v3.53.0 of the Terraform Provider. Please see the Terraform documentation on provider versioning or reach out if you need any assistance upgrading.

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[github-actions]

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