Pyspark sql function "format_string" has the wrong parameters in doc string

The pyspark sql function "format_string" has a function declaration of "def _format_string(format, cols):*"_ However, the function's doc strings describes the parameters as:

:param col: the column name of the numeric value to be formatted
:param d: the N decimal places

We want to update the doc string to accurately describe the parameters.