DOC: Add mention that mangle_dupe_cols is deprecated in user guide (#48182)
DOC: Add mention that mangle_dupe_cols is deprecated in user guide (#48182)


pandas-dev/pandas,datapythonista/pandas,pandas-dev/pandas,pandas-dev/pandas,pandas-dev/pandas,datapythonista/pandas,datapythonista/pandas,datapythonista/pandas