Docs: Julia version dropdown missing from top left menu in documentation for v0.5.2 and older

[IanButterworth]

There's no other obvious indication of the version relevant for the docs (apart from the URL), so that being missing is an obvious source of confusion

https://docs.julialang.org/en/v0.6.0/ <-present
https://docs.julialang.org/en/v0.5.2/ <-missing
https://docs.julialang.org/en/v0.4.7/ <-missing

[KristofferC]

Those docs were generated using a completely different system from the current and did not have the dropdown.

Perhaps we should inject a warning or something in the old docs to highlight that they are for old Julia versions.

[IanButterworth]

I think a warning is a good idea.. especially given how high some of the the v0.4.7 pages currently rank in google (for me at least)

[fredrikekre]

This will be fixed with the next Documenter update. In particular see #26825 (comment). Closing as dup of #26825