DOC:  Meaning of Timestamp `freq` attribute is unclear in docs
#### Problem description

The `freq` attribute of the `pandas.Timestamp` class is not well explained on the class's documentation page.  

For background, there is an existing issue #15146 which proposes removing the `freq` attribute.  I agree with that proposal, although I don't know how much technical complexity weighs against that.

If pandas decides not to deprecate/remove it, the documentation for it should be improved.  The current (version 0.24.1) documentation reads:

```
ts_input : datetime-like, str, int, float
     Value to be converted to Timestamp
freq : str, DateOffset                                <----
     Offset which Timestamp will have                 <----
tz : str, pytz.timezone, dateutil.tz.tzfile or None
    Time zone for time which Timestamp will have.
```

The `Timestamp` class or `datetime.datetime` class represents a point in time, an instant.  There is no "offset" that a time point has, semantically speaking.

As far as I can tell, the role of `freq` is (1) to provide an implicit timedelta for Timestamp + integer operations, which are now deprecated, and (2) to provide a default in `Timestamp.to_period()` when that method's `freq` argument is None.

The `freq` value does not influence equality comparisons between Timestamp objects, and does not influence the hash of a Timestamp object.  It is dropped in a few Timestamp transformations like tz localization 

It's hard for me to suggest what the documentation should be here, since the attribute seems like a vestige from the days before a Period class, and since it doesn't influence the semantic meaning of a timestamp.


 