Bug 1152171 part 3 - Update web-platform-tests expectations; r=jgraham

Until the renaming PR (https://github.com/w3c/web-platform-tests/pull/1748)
lands upstream and we update, this test will fail.

testing/web-platform/meta/web-animations/animation-timeline/idlharness.html.ini

@@ -0,0 +1,7 @@
+[idlharness.html]
+  type: testharness
+  [AnimationTimeline must be primary interface of document.timeline]
+    expected: FAIL
+
+  [Stringification of document.timeline]
+    expected: FAIL