Network timeouts can happen from time to time. Simply try again later. If the issue still persists after a few hours you could reach out to the Fedora Infrastructure Team.
Please also note that the copr repo for restic is not official. In case of issues you’d better contact the maintainer.
If you need a quick way to install restic you can always download the official binary at Github, unpack and drop it into a folder in your $PATH (e.g. /usr/local/bin). That’s all that is needed to run restic.
Result: x86_64
So I guess restic_0.9.0_linux_amd64
I just download that file to my server, extract it, rename restic_0.9.0_linux_amd64 to restic. put it in /usr/bin/ resulting in /usr/bin/restic and everything should be fine?