[BUG] Cost Management Scheduled Action API ignores dayOfMonth property

### API Spec link

https://github.com/Azure/azure-rest-api-specs/blob/8d0bc1f353f04d0cac751e6819064086c972ae99/specification/cost-management/resource-manager/Microsoft.CostManagement/stable/2024-08-01/scheduledActions.json#L873

### API Spec version

2023-08-01

### Describe the bug

Swagger indicates that [dayOfMonth](https://github.com/Azure/azure-rest-api-specs/blob/8d0bc1f353f04d0cac751e6819064086c972ae99/specification/cost-management/resource-manager/Microsoft.CostManagement/stable/2024-08-01/scheduledActions.json#L873) means that UTC day on which cost analysis data will be emailed. Must be between 1 and 31. This property is applicable when frequency is Monthly and overrides weeksOfMonth or daysOfWeek. Then I tried to set dayOfMonth to 30 while creating Cost Management Scheduled Action but seems it doesn't take effect and Azure Portal always indicates it will be triggered on the first day.

below is the request payload:
```
PUT https://management.azure.com/subscriptions/xx-xx-xx-xx/resourceGroups/acctestRG-cm-test01/providers/Microsoft.CostManagement/scheduledActions/testcostviewdzxc2

{
"kind": "Email",
"properties": {
"displayName": "CostByServiceViewdzxc2",
"fileDestination": {
"fileFormats": []
},
"notification": {
"message": "Hi",
"subject": "Cost Management Report for AzureSDKTest Subscription",
"to": [
"test@test.com",
"hashicorp@test.com"
]
},
"notificationEmail": "test@test.com",
"schedule": {
"dayOfMonth": 30,
"daysOfWeek": null,
"endDate": "2025-03-31T15:00:00Z",
"frequency": "Monthly",
"hourOfDay": 0,
"startDate": "2025-03-01T15:00:00Z",
"weeksOfMonth": null
},
"status": "Enabled",
"viewId": "/subscriptions/xx-xx-xx-xx/resourceGroups/acctestRG-cm-test01/providers/Microsoft.CostManagement/views/testcostviewdsfgdf"
}
}
```


### Expected behavior

When I try to set dayOfMonth to 30 while creating Cost Management Scheduled Action and Azure Portal should indicate that it will be triggered on 30th day.

### Actual behavior

When I try to set dayOfMonth to 30 while creating Cost Management Scheduled Action and Azure Portal indicates that it will be triggered on the first day.

### Reproduction Steps

1. Create resource group
2. Create resource group cost management view
3. Create cost management scheduled action

### Environment

PROD

Start with the scheduledActions.json specification at the linked stable/2024-08-01 path, around line 873, and inspect how the schedule's dayOfMonth property is defined and represented. Reproduce the monthly schedule request from the issue, then determine whether the specification accurately describes the service behavior; done means the contract and documented expected behavior agree.

Written by the indexing model from the issue text.