Anchor links in repo notebooks don't work

Created by: benvenker

Form slack

Anchor links in search notebooks committed to repositories don't seem to work - clicking on an anchor generates a link like this:

https://sourcegraph.com/github.com/sourcegraph/devx-scratch/-/blob/2022/support/log.snb.md#2022-06-16-45826005-6883-4201-873a-52ffc7e287ea

However, this link doesn't correctly go the desired anchor when shared

cc @bobheadxi