Update test expectations for xss-ALLOWED-parent-navigation-change.html

http/tests/security/frameNavigation/xss-ALLOWED-parent-navigation-change.html
flakes on Mac 10.13 as well,

Example build:
https://ci.chromium.org/p/chromium/builders/ci/Mac10.13%20Tests/23868

TBR: szager@chromium.org
Change-Id: I38620b071a1acdb7d0b98ef022cc4062a2304c6f
Bug: 1008826
Reviewed-on: https://chromium-review.googlesource.com/c/chromium/src/+/2154760
Commit-Queue: Sahel Sharify <sahel@chromium.org>
Reviewed-by: Sahel Sharify <sahel@chromium.org>
Cr-Commit-Position: refs/heads/master@{#760139}

third_party/blink/web_tests/TestExpectations

@@ -6008,8 +6008,7 @@ crbug.com/630695 compositing/masks/mask-with-removed-filters.html [ Pass Failure
 crbug.com/1005128 crypto/subtle/abandon-crypto-operation2.html [ Pass Crash ]
 
 # Sheriff 2019-09-27
-crbug.com/1008826 [ Retina ] http/tests/security/frameNavigation/xss-ALLOWED-parent-navigation-change.html [ Pass Failure Timeout ]
-crbug.com/1008826 [ Mac10.14 ] http/tests/security/frameNavigation/xss-ALLOWED-parent-navigation-change.html [ Pass Failure Timeout ]
+crbug.com/1008826 [ Mac ] http/tests/security/frameNavigation/xss-ALLOWED-parent-navigation-change.html [ Pass Failure Timeout ]
 
 # Sheriff 2019-09-30
 crbug.com/1003715 [ Win10 ] http/tests/notifications/serviceworker-notification-properties.html [ Pass Failure Timeout ]