DOC: clarify that read_parquet accepts a directory path
The current documentation (both docstring https://pandas.pydata.org/pandas-docs/stable/reference/api/pandas.read_parquet.html and user guide https://pandas.pydata.org/pandas-docs/stable/user_guide/io.html#partitioning-parquet-files) don't make it very clear that the file path can also be a directory name that contains multiple (partitioned) parquet files (in addition to single file path).