[BUG][Cost Management] parameter grainParameter does not work on list operations of Benefit Utilization Summaries

### API Spec link

https://github.com/Azure/azure-rest-api-specs/blob/main/specification/cost-management/resource-manager/Microsoft.CostManagement/stable/2023-11-01/costmanagement.benefits.json#L1414

### API Spec version

2023-11-01

### Describe the bug

Parameter `grainParameter` does not work when calling BenefitUtilizationSummaries_List operations as [sample](https://learn.microsoft.com/en-us/rest/api/cost-management/benefit-utilization-summaries/list-by-billing-account-id?view=rest-cost-management-2023-11-01&tabs=HTTP) showed in the docs. Response still returned with daily grain though the `grainParameter` was set as Monthly. Yet it works when have `&grain=Monthly` in the API URL.
```
https://management.azure.com/providers/Microsoft.Billing/billingAccounts/{billingAccountId}/providers/Microsoft.CostManagement/benefitUtilizationSummaries?api-version=2023-11-01&grainParameter={grainParameter}&filter={filter}
```

### Expected behavior

Update the actual parameter name `grainParameter` to `grain` to make fix on doc description as well as SDKs.

### Actual behavior

`&grain=Monthly` works yet actual parameter name `grainParameter` does not work.

### Reproduction Steps

Calling api in this format.
```
GET https://management.azure.com/providers/Microsoft.Billing/billingAccounts/{billingAccountId}/providers/Microsoft.CostManagement/benefitUtilizationSummaries?api-version=2023-11-01&grainParameter={grainParameter}&filter={filter}
```

### Environment

_No response_

Open the linked costmanagement.benefits.json specification at line 1414 and inspect the BenefitUtilizationSummaries_List parameter definition. Confirm the specification and its documentation use grain rather than grainParameter, and verify the resulting request matches the working grain=Monthly form.

Written by the indexing model from the issue text.