Mark RTCPeerConnection-track-stats.https.html no longer flaky.

Now that the bugs caused by the Resolver having updated have been fixed
in https://bugs.chromium.org/p/chromium/issues/detail?id=919035, these
tests are no longer expected to be flaky.

TBR=hta@chromium.org

Bug: 919035
Change-Id: I60c421759c69f60e620d76e862aaad5d858bc489
Reviewed-on: https://chromium-review.googlesource.com/c/1396024Reviewed-by: Henrik Boström <hbos@chromium.org>
Reviewed-by: Harald Alvestrand <hta@chromium.org>
Commit-Queue: Henrik Boström <hbos@chromium.org>
Cr-Commit-Position: refs/heads/master@{#619923}

third_party/blink/web_tests/TestExpectations

@@ -3222,10 +3222,6 @@ crbug.com/893490 [ Mac ] external/wpt/css/css-text/white-space/control-chars-09F
 crbug.com/893480 external/wpt/infrastructure/testdriver/actions/elementTiming.html [ Timeout ]
 crbug.com/893480 external/wpt/infrastructure/testdriver/actions/multiDevice.html [ Failure Timeout ]
 
-# Some tests are flaky with regards to whether or not candidate-pair stats are present.
-crbug.com/919035 external/wpt/webrtc/RTCPeerConnection-track-stats.https.html [ Pass Failure ]
-crbug.com/919035 virtual/webrtc-wpt-unified-plan/external/wpt/webrtc/RTCPeerConnection-track-stats.https.html [ Pass Failure ]
-
 # Hit a DCHECK
 crbug.com/918664 external/wpt/css/vendor-imports/mozilla/mozilla-central-reftests/sizing/block-size-with-min-or-max-content-table-1a.html [ Failure Pass ]