Bug 1560317 - delete mediasource-play-then-seek-back.html expectancy r=jmaher

Differential Revision: https://phabricator.services.mozilla.com/D35794

--HG--
extra : moz-landing-system : lando

testing/web-platform/meta/media-source/mediasource-play-then-seek-back.html.ini

@@ -1,7 +1,3 @@
 [mediasource-play-then-seek-back.html]
   disabled:
     if (os == "android") and not e10s: https://bugzilla.mozilla.org/show_bug.cgi?id=1499003
-  [Test playing then seeking back.]
-    expected:
-      if (os == "android") and debug: FAIL
-