Bug 1175768 - Remove bogus check. r=jya

dom/media/mediasource/test/test_TruncatedDuration.html

@@ -41,7 +41,6 @@ function do_seeked(e) {
   is(v.currentTime, duration, "current time was updated");
   is(v.duration, duration, "element duration was updated");
   is(v._sb.buffered.length, 1, "One buffered range");
-  is(v._sb.buffered.end(0), duration, "sourcebuffer truncated");
   // Truncated mediasource duration will cause the video element to seek.
   v.addEventListener("seeking", do_seeking, false);
 }