Fix private image links

[cvphelps]

When I copied the Readme from wandb/annotation_streamlit to examples I didn't realize that the links for the images in the markdown would be still pointing to images in the original repo.

This means that the images worked for me, because I had permissions to that private repo, but in an anonymous browser it shows broken links instead 👎

I just fixed this with fresh versions of those images, hosted in this repo instead.