Remove docs CI workflow
This PR removes the docs CI workflow, PR testing is done directly by readthedocs.
Maintenance will be performed on git.ligo.org, containers.ligo.org, and docs.ligo.org on Tuesday 2 July 2024 starting at approximately 9:30am PDT. It is expected to take around two hours and there will be several periods of downtime throughout the maintenance. Please address any comments, concerns, or questions to the helpdesk.
This PR removes the docs CI workflow, PR testing is done directly by readthedocs.