Remove references to the ancient wiki

[petebankhead]

...unless they are clearly flagged as being of historical interest.

See https://github.com/search?q=repo%3Aqupath%2Fqupath-docs%20qupath%2Fqupath%2Fwiki%2F&type=code

Specifically, we shouldn't link there for setting things up with IntelliJ, and we should link to https://github.com/qupath/qupath-gradle-scripting-project

[alanocallaghan]

We could make its archived status more explicit by removing it from the qupath repo, uploading it as a separate repo to the qupath org, and archiving it