Update test expectation for external/wpt/accelerometer/Accelerometer-iframe-access.https.html

TBR=carlosk@chromium.org
NOTRY=true

Bug: 857520
Change-Id: I319bf632a140514597272287a28682c84e38ffad
Reviewed-on: https://chromium-review.googlesource.com/1119196Reviewed-by: Yi Gu <yigu@chromium.org>
Commit-Queue: Yi Gu <yigu@chromium.org>
Cr-Commit-Position: refs/heads/master@{#571260}

third_party/WebKit/LayoutTests/TestExpectations

@@ -4743,5 +4743,5 @@ crbug.com/856969 [ Win Linux Mac ] virtual/outofblink-cors/external/wpt/fetch/ap
 # Sheriff 2018-06-28
 crbug.com/857410 [ Linux ] virtual/outofblink-cors/external/wpt/service-workers/service-worker/about-blank-replacement.https.html [ Pass Timeout ]
 crbug.com/857414 [ Win Mac10.10 Mac10.11 ] http/tests/devtools/sources/debugger-breakpoints/event-listener-breakpoints-webaudio.js [ Pass Timeout ]
-crbug.com/857520 [ Mac10.10 Mac10.13 ] external/wpt/accelerometer/Accelerometer-iframe-access.https.html [ Failure ]
+crbug.com/857520 [ Mac ] external/wpt/accelerometer/Accelerometer-iframe-access.https.html [ Failure ]
 crbug.com/856330 [ Linux Debug ] virtual/service-worker-servicification/external/wpt/service-workers/service-worker/about-blank-replacement.https.html [ Pass Timeout ]