Suggest using datasets CLI to convert to parquet in script-dataset error message

[albertvillanova]

We should suggest using the datasets CLI to convert a dataset to Parquet in our script-dataset error message, once:

• Add CLI function to convert script-dataset to Parquet datasets#6795 is merged and datasets is released and updated here.

[albertvillanova]

Fixed by:

• Update DatasetWithScriptNotSupportedError message suggesting CLI #2747