Removes link to public notebooks of sourcegraph.com (#838)

This link was resolving in an intentional 404

<!-- Explain the changes introduced in your PR -->

## Pull Request approval

You will need to get your PR approved by at least one member of the
Sourcegraph team. For reviews of docs formatting, styles, and component
usage, please tag the docs team via the #docs Slack channel.

Co-authored-by: Maedah Batool <[email protected]>

Author: danielmarquespt