Mark RTCPeerConnection-explicit-rollback-iceGatheringState as fixed

Bug: chromium:1115080, chromium:1110833
Change-Id: I6c97e05225b8dc399d94cfb0e0817577a05db285
Reviewed-on: https://chromium-review.googlesource.com/c/chromium/src/+/2368559Reviewed-by: Guido Urdaneta <guidou@chromium.org>
Commit-Queue: Harald Alvestrand <hta@chromium.org>
Cr-Commit-Position: refs/heads/master@{#801104}

third_party/blink/web_tests/TestExpectations

@@ -3069,8 +3069,6 @@ crbug.com/367760 external/wpt/svg/pservers/reftests/meshgradient-basic-001.svg [
 virtual/webrtc-wpt-plan-b/external/wpt/webrtc/RTCPeerConnection-operations.https.html [ Pass ]
 virtual/webrtc-wpt-plan-b/external/wpt/webrtc/RTCPeerConnection-restartIce-onnegotiationneeded.https.html [ Pass ]
 
-crbug.com/1110833 external/wpt/webrtc/RTCPeerConnection-explicit-rollback-iceGatheringState.html [ Timeout ]
-
 # Tests that start hanging after implementing RTCRtpTransceiver.stop
 crbug.com/1115087 external/wpt/webrtc/RTCRtpTransceiver.https.html [ Timeout ]