Update web-platform-tests URLs (WICG#136)

CONTRIBUTING.md

@@ -25,8 +25,8 @@ feature, you can remove yourself with the above syntax.
 # Tests
 
 For normative changes, a corresponding
-[web-platform-tests](https://github.com/w3c/web-platform-tests) PR is highly appreciated. Typically,
+[web-platform-tests](https://github.com/web-platform-tests/wpt) PR is highly appreciated. Typically,
 both PRs will be merged at the same time. Note that a test change that contradicts the spec should
 not be merged before the corresponding spec change. If testing is not practical, please explain why
-and if appropriate [file an issue](https://github.com/w3c/web-platform-tests/issues/new) to follow
+and if appropriate [file an issue](https://github.com/web-platform-tests/wpt/issues/new) to follow
 up later. Add the `type:untestable` or `type:missing-coverage` label as appropriate.

test/index.bs

@@ -28,7 +28,7 @@ interface does not permit arbitrary control over the behavior of devices. Some
 parameters are configurable and some are specified.
 
 The only intended client of this API are tests in
-<a href="https://github.com/w3c/web-platform-tests">Web Platform Tests</a>.
+<a href="https://github.com/web-platform-tests/wpt">Web Platform Tests</a>.
 This testing
 API will be changed as needed to support the evolution of those tests.