DOC: Fix EX02 in pandas.Index.get_loc
- [ ] closes #xxxx
- [ ] tests added / passed
- [x] passes `black pandas`
- [x] passes `git diff upstream/master -u -- "*.py" | flake8 --diff`
- [ ] whatsnew entry

Related to #27977. 

```
################################################################################
################################## Validation ##################################
################################################################################

5 Errors found:
        No extended summary found
        Parameter "key" has no description
        The first line of the Returns section should contain only the type, unless multiple values are being returned
        Return value has no description
        See Also section not found
```
Also, adding 
```
xref #27977
```
to the pull request description would be good > Thanks @farhanreynaldo
> 
> In the future I think it would help to also post the output of
> 
> ```
> python scripts/validate_docstrings.py pandas.Index.get_loc
> ```
> 
> which here is
> 
> ```
> ################################################################################
> ################################## Validation ##################################
> ################################################################################
> 
> 5 Errors found:
>         No extended summary found
>         Parameter "key" has no description
>         The first line of the Returns section should contain only the type, unless multiple values are being returned
>         Return value has no description
>         See Also section not found
> ```
> 
> to show that the doctests now pass

Thank you for the reminder, @MarcoGorelli, I will add it next time. Great thanks @farhanreynaldo for PR and @MarcoGorelli for review