AWS::Neptune::DBCluster doesn't support CopyTagsToSnapshot

### Name of the resource

AWS::Neptune::DBCluster

### Resource name

_No response_

### Description

CloudFormation does not support the CopyTagsToSnapshot property on AWS::Neptune::DBCluster. I can see from a previous submitted issue that this was also a missing property for AWS::DocDB::DBCluster and AWS::RDS::DBCluster. Just wanting to bring awareness to this.

### Other Details

[Neptune API CreateDBCluster docs](https://docs.aws.amazon.com/neptune/latest/userguide/api-clusters.html#CreateDBCluster)

Start with the issue description and the linked Neptune CreateDBCluster API documentation to confirm the CopyTagsToSnapshot property and its behavior. The payload names no repository files or tests, so investigate the CloudFormation coverage process and comparable DBCluster requests. Done means the requested property is supported for AWS::Neptune::DBCluster and its coverage is verified.

Written by the indexing model from the issue text.