azurerm_healthcare_dicom_service, azurerm_healthcare_fhir_service - fix identity schema in in data source

[xiaxyi]

opening a new pr to include the changes in #21578
fix #21538

--- PASS: TestAccHealthCareFhirServiceDataSource_identity (802.85s)
PASS
ok      github.com/hashicorp/terraform-provider-azurerm/internal/services/healthcare    803.675s

--- PASS: TestAccHealthcareApiFhirService_updateIdentity (1363.88s)
PASS
ok      github.com/hashicorp/terraform-provider-azurerm/internal/services/healthcare    1365.231s

[catriona-m]

Thanks @xiaxyi LGTM!

[github-actions]

This functionality has been released in v3.55.0 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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