DEP: Enforce deprecation of mangle_dupe_cols
#48137
Thanks @phofl  The pull request says

> Deprecating `mangle_dupe_cols`, which was never implemented, and will be replaced by a new standard argument to allow change the format of the renamed columns.

Which is the new standard argument for this? In https://pandas.pydata.org/docs/reference/api/pandas.read_csv.html I cannot find any option for dealing with duplicate column names in `pd.read_csv`