Fix pandas DtypeWarning in download_demo

[amontanez24]

Environment Details

Please indicate the following details about the environment in which you found the bug:

• SDV version: Current
• Python version: Any
• Operating System: Any

Error Description

Sometimes when calling download_demo, the following warning pops up:

demo.py:99: DtypeWarning: Columns (7) have mixed types. Specify dtype option on import or set low_memory=False.
  data[table_name] = pd.read_csv(io.StringIO(file_.decode()))

This is annoying but also means the dtypes might be incorrectly inferred by pandas.

Steps to reproduce

datasets = get_available_demos('multi_table')
for dataset_name in datasets['dataset_name']:
    metadata, tables = download_demo(modality, dataset_name)