Fix the hub user name in a longformer doctest checkpoint
# What does this PR do?

`jpelhaw` not exist on hub, and test fails at this moment.

Run locally with this PR: doctest pass for this model now.
cc @ArthurZucker <|||||>_The documentation is not available anymore as the PR was closed or merged._<|||||>Checked with the last run (May 18th -- sorry I should check doctest status much earlier), it worked with the previous checkpoint string, which suggests that the user renamed since then.

I agree with you regarding `not the most strategic thing` (I raised the doubt before, but we decided to continue with this approach to see how things go)<|||||>@LysandreJik just reminded me that the migration to the new cache system on huggingface_hub will magically support repo renames so this won't be a problem in the future!