Move customResponseHeaders to beta only

[c2thorn]

Fixes hashicorp/terraform-provider-google#7299

customResponseHeaders only appears in the beta Compute API, and should be removed from the GA provider.

If this PR is for Terraform, I acknowledge that I have:

• Searched through the issue tracker for an open issue that this either resolves or contributes to, commented on it to claim it, and written "fixes {url}" or "part of {url}" in this PR description. If there were no relevant open issues, I opened one and commented that I would like to work on it (not necessary for very small changes).
• Generated Terraform, and ran make test and make lint to ensure it passes unit and linter tests.
• Ensured that all new fields I added that can be set by a user appear in at least one example (for generated resources) or third_party test (for handwritten resources or update tests).
• Ran relevant acceptance tests (If the acceptance tests do not yet pass or you are unable to run them, please let your reviewer know).
• Read the Release Notes Guide before writing my release note below.

Release Note Template for Downstream PRs (will be copied)

compute: removed `custom_response_headers` from GA `google_compute_backend_service` since it only works in the Beta version

[modular-magician]

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

Diff report:

Terraform GA: Diff ( 4 files changed, 4 insertions(+), 145 deletions(-))
Terraform Beta: Diff ( 2 files changed, 8 insertions(+), 7 deletions(-))
Ansible: Diff ( 2 files changed, 19 deletions(-))
TF Conversion: Diff ( 1 file changed, 11 deletions(-))
TF OiCS: Diff ( 1 file changed, 3 insertions(+))
Inspec: Diff ( 2 files changed, 2 insertions(+), 2 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=161103"

[c2thorn]

/gcbrun

[modular-magician]

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

Diff report:

Terraform GA: Diff ( 4 files changed, 4 insertions(+), 145 deletions(-))
Terraform Beta: Diff ( 2 files changed, 8 insertions(+), 7 deletions(-))
Ansible: Diff ( 2 files changed, 19 deletions(-))
TF Conversion: Diff ( 1 file changed, 11 deletions(-))
TF OiCS: Diff ( 1 file changed, 3 insertions(+))
Inspec: Diff ( 2 files changed, 2 insertions(+), 2 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=161502"

[modular-magician]

I have triggered VCR tests in RECORDING mode for the following tests that failed during VCR: TestAccDataSourceComposerEnvironment_basic|TestAccDataSourceComputeResourcePolicy|TestAccDataSourceSpannerInstance_basic|TestAccNotebooksInstanceIamMemberGenerated|TestAccNotebooksInstanceIamPolicyGenerated|TestAccActiveDirectoryDomainTrust_activeDirectoryDomainTrustBasicExample|TestAccBigqueryDataTransferConfig|TestAccCloudSchedulerJob_schedulerJobHttpExample|TestAccComposerEnvironment_withUpdateOnCreate|TestAccComputeBackendService_backendServiceCacheExample|TestAccComputeBackendService_backendServiceNetworkEndpointExample|TestAccComputeGlobalForwardingRule_globalForwardingRuleHttpExample|TestAccComputeGlobalForwardingRule_globalForwardingRuleInternalExample|TestAccComputeManagedSslCertificate_managedSslCertificateBasicExample|TestAccComputeRegionBackendService_regionBackendServiceCacheExample|TestAccComputeTargetGrpcProxy_targetGrpcProxyBasicExample|TestAccComputeTargetGrpcProxy_update|TestAccComputeTargetHttpProxy_targetHttpProxyBasicExample|TestAccComputeTargetHttpsProxy_targetHttpsProxyBasicExample|TestAccComputeUrlMap_urlMapBasicExample|TestAccComputeUrlMap_urlMapTrafficDirectorRouteExample|TestAccComputeUrlMap_urlMapTrafficDirectorRoutePartialExample|TestAccComputeUrlMap_urlMapTrafficDirectorPathExample|TestAccComputeUrlMap_urlMapHeaderBasedRoutingExample|TestAccComputeUrlMap_urlMapTrafficDirectorPathPartialExample|TestAccComputeUrlMap_urlMapParameterBasedRoutingExample|TestAccComputeUrlMap_defaultRouteActionTrafficDirectorPathUpdate|TestAccComputeUrlMap_defaultRouteActionTrafficDirectorUpdate|TestAccComputeUrlMap_trafficDirectorPathUpdate|TestAccFirestoreDocument_firestoreDocumentBasicExample|TestAccFirestoreDocument_firestoreDocumentNestedDocumentExample|TestAccFirestoreDocument_update|TestAccFilestoreInstance_filestoreInstanceBasicExample|TestAccFilestoreInstance_update|TestAccNotebooksEnvironment_notebookEnvironmentBasicExample|TestAccNotebooksInstance_notebookInstanceBasicExample|TestAccNotebooksInstance_notebookInstanceBasicGpuExample|TestAccNotebooksInstance_notebookInstanceBasicContainerExample|TestAccNotebooksInstance_notebookInstanceFullExample|TestAccOSLoginSSHPublicKey_osLoginSshKeyExpiry|TestAccStorageBucket_lifecycleRuleStateLive|TestAccStorageBucket_lifecycleRuleStateAny You can view the result here: "https://ci-oss.hashicorp.engineering/viewQueued.html?itemId=161505"