fix(docs): oidc-jans-script.py fails to find existing user during authentication and creates duplicate records.

I've recently setup the person_authentication oidc-jans-script.py custom script in my project and I found whenever reauthenticating a new user was being created even when the user record already existed.

I found through debugging that the user service fails to find the record, even though the value for `jansExtUid` is exactly the same as the existing record.

I believe the problem exists at the line of code below:

https://github.com/JanssenProject/jans/blob/7f82250ca36d05ae3c0ab8f5ea13ba0d0dc3f4b7/docs/script-catalog/person_authentication/oidc/oidc-jans-script.py#L282C48-L282C48

I'm not 100% familiar with this project, but I think this line of code:
```python
foundUser = userService.getUserByAttribute("jansExtUid", "oidc:"+userId)
```

should be:
```python
foundUser = userService.getUserByAttribute("jansExtUid", "oidc:"+userId, True)
```

After using the overloaded function and setting the `multiValued` paramater to `True` it solves the problem.

I think `jansExtUid` may have previously not have been multivalued but now is and the oidc script may be out of date.