Is `table_id` for backups if it came from `DescribeTable`?

### Describe the issue

This documentation appears to be saying that the `table_id` that came back from `DescribeTable` is referencing a table which was backed up. That doesn't seem right, it seems like it should just say that it's a unique identifier for the table.

I think this is where it is in the repo: https://github.com/awslabs/aws-sdk-rust/blob/2ebc092a0372b5f1508b26845c0cf88f537d29b7/sdk/dynamodb/src/types/_table_description.rs#L61

I think it might be self-explanatory, but it's still room for improvement.

If I'm wrong, and this is _not_ self-explanatory, please also let me know.

### Links

https://docs.rs/aws-sdk-dynamodb/0.27.0/aws_sdk_dynamodb/types/struct.TableDescription.html#method.table_id

Read sdk/dynamodb/src/types/_table_description.rs around line 61 and compare the table_id description with the DescribeTable API meaning and the linked docs.rs page. Done means the wording clearly and accurately describes table_id as the table's unique identifier, or confirms that the existing backup-related wording is correct.

Written by the indexing model from the issue text.