doc: Use non-shallow clone on readthedocs
Since some part of the documentation are generated from the git history, use a non-shallow clone.
GitLab Maintenance scheduled for Thursday, 18th December 2025, from 7:00 AM to 10:00 AM BST. GitLab will be in read-only mode and experience short periods of complete downtime (up to 20 minutes) during this window.
Since some part of the documentation are generated from the git history, use a non-shallow clone.