Updated labels for cloud run domain mapping diff suppress

[modular-magician]

Resolved hashicorp/terraform-provider-google#8934. Permadiff due to a new label that gets set by GCP.

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Release Note Template for Downstream PRs (will be copied)

cloudrun: fixed permadiff on `google_cloud_run_domain_mapping.metadata.labels`

Derived from GoogleCloudPlatform/magic-modules#4720