Improve RedCaps dataset card
The docs for this PR live [here](https://moon-ci-docs.huggingface.co/docs/datasets/pr_4100). All of your documentation changes will be reflected on that endpoint.
This PR modifies the RedCaps card to:
* fix the formatting of the Point of Contact fields on the Hub
* speed up the image fetching logic (aligns it with the [img2dataset](https://github.com/rom1504/img2dataset) tool) and make it more robust (return None if **any** exception is thrown)