Remove WoodworkColumnAccessor.set_logical_type method

In PR #590 the `set_logical_types` method was added to the WoodworkColumnAccessor. This method returns a new series using the `init_series` helper function. This call is made to handle any dtype changes that might be needed as a result of the LogicalType change.

Since this method just calls `ww.init_series`, we should review whether it is useful to retain this extra method as an alternative to `init_series` or would it be sufficient just to direct users to use the `init_series` function any time a dtype change is needed on a series. If we remove this method we would be able to simplify the code in `column_accessor.py` as well as remove the corresponding tests from `test_column_accessor.py`.