Prevent permadiff on monitoring_uptime_check_config

[modular-magician]

Fixes a permadiff on uptime check config which causes it to be recreated every time.

The labels property in the monitored_resource property should ignore changes to the project_id label if not set by the user. GCP sets the project_id and that causes the resource to exhibit a diff and get recreated every time.

fixes #18038

Release Note Template for Downstream PRs (will be copied)

monitoring: fixed a permadiff with `monitored_resource.labels` property in the `google_monitoring_uptime_check_config` resource

Derived from GoogleCloudPlatform/magic-modules#10694

[github-actions]

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