Update web-platform-tests URLs (#444)

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.

index.bs

@@ -17,7 +17,7 @@ Former Editor: Ian Hickson, Google http://www.google.com/, ian@hixie.ch
 !Participate: <a href=https://github.com/w3c/webvtt>GitHub w3c/webvtt</a> (<a href=https://github.com/w3c/webvtt/issues/new>new issue</a>, <a href=https://github.com/w3c/webvtt/issues>open issues</a>, <a href=https://www.w3.org/Bugs/Public/buglist.cgi?product=TextTracks%20CG&component=WebVTT&resolution=--->legacy open bugs</a>)
 !Commits: <a href=https://github.com/w3c/webvtt/commits>GitHub w3c/webvtt/commits</a>
 !Commits: <a href=https://twitter.com/webvtt>@webvtt</a>
-Test Suite: https://github.com/w3c/web-platform-tests/tree/master/webvtt
+Test Suite: https://github.com/web-platform-tests/wpt/tree/master/webvtt
 Abstract: This specification defines WebVTT, the Web Video Text Tracks format. Its main use is for marking up external text track resources in connection with the HTML &lt;track> element.
 Abstract: WebVTT files provide captions or subtitles for video content, and also text video descriptions [[MAUR]], chapters for content navigation, and more generally any form of metadata that is time-aligned with audio or video content.
 Boilerplate: omit conformance, omit feedback-header

index.html

@@ -1455,7 +1455,7 @@ <h2 class="no-num no-toc no-ref heading settled" id="subtitle"><span class="cont
      <dt>Latest published version:
      <dd><a href="https://www.w3.org/TR/webvtt1/">https://www.w3.org/TR/webvtt1/</a>
      <dt>Test Suite:
-     <dd><a href="https://github.com/w3c/web-platform-tests/tree/master/webvtt">https://github.com/w3c/web-platform-tests/tree/master/webvtt</a>
+     <dd><a href="https://github.com/web-platform-tests/wpt/tree/master/webvtt">https://github.com/web-platform-tests/wpt/tree/master/webvtt</a>
      <dt class="editor">Editor:
      <dd class="editor p-author h-card vcard"><a class="p-name fn u-email email" href="mailto:silvia.pfeiffer@data61.csiro.au">Silvia Pfeiffer</a> (<a class="p-org org" href="https://www.csiro.au/">CSIRO</a>)
      <dt class="editor">Former Editors: