Infra links to web-platform-tests, but probably shouldn't

[annevk]

This is because we baked it into the Bikeshed template.

cc @domenic

[domenic]

This should be fixable by adding something like !Tests: to the header. Although I'm not sure if making the value an empty string will cause a deletion. If it doesn't then we may have a Bikeshed feature request.

[domenic]

Because of my previous Bikeshed feature request at speced/bikeshed#1161, !Tests: does not work; that just merges an empty item with the existing list. I'll file a new feature request.

[wooorm]

To add to this, the tests URL (https://github.com/web-platform-tests/wpt/tree/master/infra) is also dead currently!