fixed maintenance_exclusion deletion

[edwardmedia]

Fixes hashicorp/terraform-provider-google#8566

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Release Note Template for Downstream PRs (will be copied)

container: Fixed failure in deleting `maintenance_exclusion` for `google_container_cluster`

[modular-magician]

Hi! I'm the modular magician. Your PR generated some diffs in downstreams - here they are.

Diff report:

Terraform GA: Diff ( 2 files changed, 6 insertions(+), 8 deletions(-))
Terraform Beta: Diff ( 2 files changed, 6 insertions(+), 8 deletions(-))

[modular-magician]

I have triggered VCR tests based on this PR's diffs. See the results here: "https://ci-oss.hashicorp.engineering/viewQueued.html?itemId=174616"

[modular-magician]

I have triggered VCR tests in RECORDING mode for the following tests that failed during VCR: TestAccContainerCluster_withMaintenanceExclusionWindow|TestAccServiceUsageConsumerQuotaOverride_regionConsumerQuotaOverrideExample You can view the result here: "https://ci-oss.hashicorp.engineering/viewQueued.html?itemId=174707"