Make workload_metadata_config computed

[c2thorn]

Fixes hashicorp/terraform-provider-google#6652

workload_metadata_config is returned from the API and persisted to state while Terraform thinks it's a non-computed field.

Release Note Template for Downstream PRs (will be copied)

container: fixed an issue in `google_container_cluster` where `workload_metadata_config` would cause a permadiff

[modular-magician]

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

Diff report:

Terraform Beta: Diff ( 1 file changed, 1 insertion(+))

[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=123046"

[modular-magician]

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

Diff report:

Terraform Beta: Diff ( 1 file changed, 1 insertion(+))

[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=123190"

[modular-magician]

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

Diff report:

Terraform Beta: Diff ( 1 file changed, 1 insertion(+))

[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=123226"

[modular-magician]

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

Diff report:

Terraform Beta: Diff ( 1 file changed, 1 insertion(+))

[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=123231"

[modular-magician]

I have triggered VCR tests in RECORDING mode for the following tests that failed during VCR: TestAccFolderIamAuditConfig_multiple You can view the result here: "https://ci-oss.hashicorp.engineering/viewQueued.html?itemId=123233"