Currently on readthedocs the only documentation version is https://slicer.readthedocs.io/en/latest/
“latest” refers to the very latest Slicer Preview Release that is updated every day. Older versions are documented on the old Slicer wiki, for example https://www.slicer.org/wiki/Documentation/4.10/ScriptRepository
Since we plan to release the current Slicer Preview Release as the new stable version very soon, I would recommend you to switch to the latest Slicer Preview Release now.