Update DatasetWithScriptNotSupportedError message suggesting CLI
Suggest using the `datasets` convert_to_parquet CLI instead of opening a Discussion.

Additionally, this PR sets a default error message, instead of repeating the same everywhere.

Fix #2742.
Update DatasetWithScriptNotSupportedError message suggesting CLI: Suggest using the `datasets` convert_to_parquet CLI instead of opening a Discussion.

Additionally, this PR sets a default error message, instead of repeating the same everywhere.

Fix #2742.