Bug 1293159: Update expected results. r=gerald

The test should pass now, we do not need different expected results file.

MozReview-Commit-ID: Cl3GBRx1ISN

--HG--
extra : rebase_source : 59a90e20ada254b2a4c65bca34b21cde58a11b0c

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

@@ -1,6 +0,0 @@
-[mediasource-play-then-seek-back.html]
-  type: testharness
-  prefs: [media.mediasource.enabled:true]
-  disabled:
-    if (os == "linux"): https://bugzilla.mozilla.org/show_bug.cgi?id=1293159
-