Bug 1504529 [wpt PR 13908] - Update wpt metadata, a=testonly

wpt-pr: 13908
wpt-type: metadata

testing/web-platform/meta/webrtc/RTCPeerConnection-setRemoteDescription-rollback.html.ini

@@ -1,7 +1,4 @@
 [RTCPeerConnection-setRemoteDescription-rollback.html]
-  [setRemoteDescription(rollback) in have-remote-offer state should revert to stable state]
-    expected: FAIL
-
   [Test onsignalingstatechange event for setRemoteDescription(rollback) in have-remote-offer state should revert to stable state]
     expected: TIMEOUT