TYP: clean notations in the wrong place
https://github.com/pandas-dev/pandas/blob/master/pandas/core/groupby/groupby.py#L1294

```
# To track operations that expand dimensions, like ohlc
OutputFrameOrSeries = TypeVar("OutputFrameOrSeries", bound=NDFrame)
```

at the very least this should be in `pandas._typing`. puzzled why we need this at *all*, as this is the same as `FrameOrSeries`