How do I prevent auto-generated links in the GitHub wiki?

Update Nov. 2021, VSCode 1.63:

This issue should be allievated with issue 136198 “markdown preview wrongly creates links “

While "markdown.preview.linkify": false will disable linkify features entirely, setting md.linkify.fuzzyLink to false will disable it only for links without http(s) header.
Which, I think, is a better alternative, and it’s already supported by markdown-it.

Original answer (2014):
This isn’t limited to wiki page, and is part of the GFM (GitHub Flavored Markdown) url autolinking feature.

Putting them in “ can work but display the url as a code: foo http://example.com bar.

foo `http://example.com` bar

Another trick (mentioned in this gist) is

ht<span>tp://</span>example.com 

That will display http://example.com as regular text.

In your case (without the http://)

w<span>ww.</span>foobar.com

That would also display www.foobar.com as regular text.

geekley adds in the comments:

For emails, you can use foo<span>@</span>example.com

Venryx suggests in the comments a shorter/cleaner solution:

Just add one of the void element tags (I prefer <area>), at a location that breaks the URL detectability, eg. right before the first dot.

Example: www<area>.foobar.com