docs/resource/aws_transfer_server: Add `VPC` for endpoint_type to transfer_server (#15373)
docs/resource/aws_transfer_server: Add `VPC` for endpoint_type to transfer_server (#15373)

Document `VPC` value for endpoint_type attribute in transfer_server resource.

I put `VPC_ENDPOINT` in parentheses because it is no longer possible to create this type of Transfer servers in AWS dashboard. It is only accessible via the API, so I believe it will be eventually deprecated, but I didn't find any information to support that.
terraform-providers/terraform-provider-aws,terraform-providers/terraform-provider-aws,terraform-providers/terraform-provider-aws,terraform-providers/terraform-provider-aws