DOC: Validation of docsting validates Python type doc
Our script `scripts/validate_docstrings.py` validates that docstrings in our code follow certain standards (the right parameters are documented, the docstring contain examples, capitalization and punctuation...).

There is currently one case when the validation is incorrect. See this (hypothetical) example:
```python
class Series:
    ndim = 1
```

If we execute `./scripts/validate_docstrings.py pandas.Series.ndim`, we'd expect the script to detect that `ndim` doesn't have a docstring. But instead, the script is validating the docstring of the type `int` (the doc of the scalar `1`).

This is happening in practice for `offset`, and is preventing us to validate some error types to the CI. See: https://github.com/pandas-dev/pandas/issues/26982#issuecomment-505499869

We should detect this case in the script, and not validate the docstrings of attributes.