I noticed this wiki earlier when https://gerrit.wikimedia.org/r/227918 was going through
It has 9 pages: Main Page, User:Hydriz, User:Hydriz/vector.css, User:Hydriz/vector.js, User:Meno25, User:Riley Huntley/vector.js, User talk:Meno25, User talk:ShanmugamTesting, and User talk:ShanmugamTest
These don't seem very important.
If you exclude newusers, there's only been 22 log entries (and there's only 20 revisions and 1 archived revision). If you also exclude usermerge, renameuser, and patrol, only 7 (2 of which are related to the protection of the main page, the rest are 4 moves and a deletion related to user renames).
Basically it's unused, and I don't know if there's still a reason to keep it around.
If we decide to keep it, we should either disable VE there or fix RESTBase+Parsoid.