Bug 1476927: Enable the pref for implicit keyframes in animation-001.html.ini. r=birtles

MozReview-Commit-ID: 5JIc497ARuQ

testing/web-platform/meta/css/css-logical/animation-001.html.ini

@@ -1,4 +1,5 @@
 [animation-001.html]
+  prefs: [dom.animations-api.implicit-keyframes.enabled:true]
   [Logical shorthands follow the usual prioritization based on number of component longhands]
     expected: FAIL
     bug: https://bugzilla.mozilla.org/show_bug.cgi?id=1289155, https://bugzilla.mozilla.org/show_bug.cgi?id=1370404