doc path typo

https://cblab-documentation.readthedocs.io/en/latest/content/cbdata/cbdata.html
> The code in /CBData/input_data_transformation is our implemented pipeline to transform the raw road network to the inputs for simulation.
> 
> To begin with, put the three files in CBData/unify_data/roadnet/data.

unify_data -> input_data_transformation  or input_data_transformation  -> unify_data