Add accelerators to workstation update masks (#8979)

* Add accelerators to workstation update masks

This was missed in #8490, and so in-place updates to accelerators are silently dropped.

Verified the issue by updating my workstation config with accelerators but the actual config did not change. On inspecting the debug logs, I noticed the update mask was wrong. Near the end of the log, the following warning message was present.

```
2023-09-16T04:38:23.768Z [WARN]  Provider "provider[\"registry.terraform.io/hashicorp/google-beta\"]" produced an unexpected new value for google_workstations_workstation_config.sidb, but we are tolerating it because it is using the legacy plugin SDK.
    The following problems may be the cause of any confusing errors from downstream operations:
      - .etag: was cty.StringVal("...."), but now cty.StringVal("...")
      - .host[0].gce_instance[0].accelerators: block count changed from 1 to 0
```

* Fix test failure

mmv1/products/workstations/WorkstationConfig.yaml

@@ -198,6 +198,7 @@ properties:
       - 'host.gceInstance.shieldedInstanceConfig.enableVtpm'
       - 'host.gceInstance.shieldedInstanceConfig.enableIntegrityMonitoring'
       - 'host.gceInstance.confidentialInstanceConfig.enableConfidentialCompute'
+      - 'host.gceInstance.accelerators'
     properties:
       - !ruby/object:Api::Type::NestedObject
         name: 'gceInstance'