DOC: Fixed type hints for GroupBy.{any, all}
The current documentation says the return value of GroupBy.all and GroupBy.any is `bool`.

```
    def any(self, skipna: bool = True):
        """
        Return True if any value in the group is truthful, else False.

        Parameters
        ----------
        skipna : bool, default True
            Flag to ignore nan values during truth testing.

        Returns
        -------
        bool
        """
```

However, the actual returned type is DataFrame or Series (with the same shape as `GroupBy.sum()`).

```
In [25]: df
Out[25]:
     0    1    2    3
0  1.0  0.0  0.0  0.0
1  0.0  1.0  0.0  0.0
2  0.0  0.0  1.0  0.0
3  0.0  0.0  0.0  1.0

In [26]: df.groupby(0).any()
Out[26]:
         1      2      3
0
0.0   True   True   True
1.0  False  False  False

In [27]: type(df.groupby(0).any())
Out[27]: pandas.core.frame.DataFrame
```

This PR fixes the wrong type hints for `GroupBy.{any, all}`.

- [ ] closes #xxxx
- [ ] tests added / passed
- [x] passes `black pandas`
- [x] passes `git diff upstream/master -u -- "*.py" | flake8 --diff`
- [ ] whatsnew entry
