Bug 1564633 [wpt PR 17537] - Update interfaces/performance-timeline.idl, a=testonly

Automatic update from web-platform-tests
Update interfaces/performance-timeline.idl (#17537)

Source: https://github.com/tidoust/reffy-reports/blob/2b3480f/whatwg/idl/performance-timeline.idl
Build: https://travis-ci.org/tidoust/reffy-reports/builds/551020459
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wpt-commits: ef22f8e79aecae3a6409f0f3d984778e1fa2f8a4
wpt-pr: 17537

testing/web-platform/tests/interfaces/performance-timeline.idl

@@ -32,7 +32,6 @@ interface PerformanceObserver {
 dictionary PerformanceObserverInit {
   sequence<DOMString> entryTypes;
   DOMString type;
-  boolean buffered;
 };
 
 [Exposed=(Window,Worker)]