[Integrating libraries] Update links

[NielsRogge]

This PR updates some non-existent links of https://huggingface.co/docs/hub/en/models-adding-libraries.

• https://allennlp.org/
• https://rwightman.github.io/pytorch-image-models/

[HuggingFaceDocBuilderDev]

The docs for this PR live here. All of your documentation changes will be reflected on that endpoint. The docs are available until 30 days after the last update.

[Wauplin]

Thanks for the suggestion @NielsRogge!

As @Vaibhavs10 said, I think it's best to update these links in the current rework to avoid conflicts. I've pushed https://github.com/huggingface/hub-docs/pull/1442/commits/13487a8b51ffa6b9d05b5716aad119865b298949 to update the links. (so this PR can be closed?)

[NielsRogge]

Thanks! Closing this one.