[BUG] 'api_gateway_resource.py' does not update binary_media_types for existing API Gateway resources

[Nicat-Qrbnv]

Describe the bug
binary_media_types configuration is applied only when creating a new API Gateway. Updating an existing API Gateway does not apply changes to binary_media_types defined in metadata.

To Reproduce

1. Deploy an API Gateway without binary_media_types.
2. Add binary_media_types to the API Gateway metadata:

binary_media_types:
  - application/pdf
  - application/octet-stream