DOC: improving example
- [x] closes #45222

This is a minimal fix: the example with strange output is replaced (even if the underlying problem is not fixed/should be fixed)

Now the output in the current version is:

```
Index([None, NaT, True], dtype='object')
```



@jreback I've proposed a fix for repr-issue in #45283. Not sure it is good to make such a change  shortly before release (and thus this much more minimal PR) also probably some discussion needed  what is actually the desired and consistent behavior (probably not only series are affected). closing in favor of #45283  > @jreback I've proposed a fix for repr-issue in #45283. Not sure it is good to make such a change shortly before release (and thus this much more minimal PR) also probably some discussion needed what is actually the desired and consistent behavior (probably not only series are affected).

yeah i think your change is fine