Disabling broken fast/harness/internals-observe-gc.html.

This should be re-enabled when the root cause is found.

Tbr: mythria@chromium.org
Bug: 1011515
Change-Id: I563e102241896021f1b0837953db00c958097aba
Reviewed-on: https://chromium-review.googlesource.com/c/chromium/src/+/1844953Reviewed-by: Patrik Höglund <phoglund@chromium.org>
Commit-Queue: Patrik Höglund <phoglund@chromium.org>
Cr-Commit-Position: refs/heads/master@{#703238}

third_party/blink/web_tests/TestExpectations

@@ -6137,7 +6137,7 @@ crbug.com/1003055 virtual/threaded/external/wpt/css/css-scroll-snap/scroll-targe
 crbug.com/1003055 virtual/threaded/external/wpt/css/css-scroll-snap/scroll-target-snap-003.html [ Failure ]
 
 # Sheriff 2019-09-12
-crbug.com/1003268 [ Win10 ] fast/harness/internals-observe-gc.html [ Failure ]
+crbug.com/1003268 [ Win10 Win7 ] fast/harness/internals-observe-gc.html [ Failure ]
 crbug.com/731018 [ Mac ] external/wpt/accelerometer/Accelerometer.https.html [ Pass Failure ]
 crbug.com/731018 [ Mac ] external/wpt/gyroscope/Gyroscope.https.html [ Pass Failure ]
 crbug.com/731018 [ Mac ] external/wpt/orientation-sensor/AbsoluteOrientationSensor.https.html [ Pass Failure ]