Stop using the wiki

[eitsupi]

The wiki has not been updated for a long time and needs to be replaced by the Rocker Project website.

Since the wiki may still be referenced as like rocker-org/rocker-versioned2#875, I think it is necessary to display a warning on the wiki and lock it so that it cannot be edited.

[eitsupi]

I have added warnings and restricted editing of the wiki.

[eitsupi]

This line should be updated too.
https://github.com/rocker-org/rocker-versioned2/blob/99aa645cc08741a15af6a852d7f611d10b5fc903/build/reports/wiki_home.Rmd#L129