[contain-3] Remove WPT metadata from diff spec

Author: mirisuzanne

css-contain-3/Overview.bs

@@ -17,7 +17,6 @@ Editor: Vladimir Levin, Google, vmpstr@google.com, w3cid 75295
 Editor: Miriam E. Suzanne, Invited Expert, http://miriamsuzanne.com/contact, w3cid 117151
 Abstract: This CSS module describes the 'contain' property, which indicates that the element's subtree is independent of the rest of the page. This enables heavy optimizations by user agents when used well.
 Test Suite: https://test.csswg.org/harness/results/css-contain-1_dev/
-WPT Path Prefix: css/css-contain/
 At risk: [=style containment=] and the ''contain: style'' value
 </pre>
 <pre class="anchors">