[AWS::SageMaker::Domain] - [Coverage] - Missing support to HiddenInstanceTypes property in StudioWebPortalSettings on CloudFormation

### Name of the resource

AWS::SageMaker::Domain

### Resource name

_No response_

### Description

[AWS::SageMaker::Domain StudioWebPortalSettings](https://docs.aws.amazon.com/AWSCloudFormation/latest/UserGuide/aws-properties-sagemaker-domain-studiowebportalsettings.html) currently does not support ` HiddenInstanceTypes ` property.

This is supported in [API](https://docs.aws.amazon.com/sagemaker/latest/APIReference/API_StudioWebPortalSettings.html) and CLI
[create-domain](https://awscli.amazonaws.com/v2/documentation/api/latest/reference/sagemaker/create-domain.html)
[update-domain](https://awscli.amazonaws.com/v2/documentation/api/latest/reference/sagemaker/update-domain.html)

When using the `HiddenInstanceTypes` property, CloudFormation gives the following error:
```
[#/DefaultUserSettings/StudioWebPortalSettings: extraneous key [HiddenInstanceTypes] is not permitted]
```

Sample template to replicate the issue:
```
Resources:
SageMakerResource:
Type: AWS::SageMaker::Domain
Properties:
AuthMode: IAM
DefaultUserSettings:
StudioWebPortalSettings:
HiddenInstanceTypes:
- ml.r6id.32xlarge
DomainName: domainname
SubnetIds:
- subnet-abc
VpcId: vpc-abc
```

### Other Details

_No response_

Start with the AWS::SageMaker::Domain StudioWebPortalSettings documentation and the provided CloudFormation template, then compare them with the linked SageMaker API and create-domain/update-domain references. Done means HiddenInstanceTypes is accepted in that nested property and the sample no longer produces the extraneous-key validation error.

Written by the indexing model from the issue text.