sheriff: Disable snav-focusless-interested-element-indicated.html

Causing failures on mac.

TBR=hayato@chromium.org

Bug: 970135
Change-Id: Ib8b96084ad5bfee19cabbe011524c7fa8419bf46
Reviewed-on: https://chromium-review.googlesource.com/c/chromium/src/+/1642611Reviewed-by: Darren Shen <shend@chromium.org>
Commit-Queue: Darren Shen <shend@chromium.org>
Cr-Commit-Position: refs/heads/master@{#665832}

third_party/blink/web_tests/TestExpectations

@@ -5833,3 +5833,6 @@ crbug.com/966345 external/wpt/webvtt/rendering/cues-with-video/processing-model/
 crbug.com/905971 virtual/blink-cors/http/tests/security/img-redirect-to-crossorigin-credentials.html [ Failure ]
 crbug.com/905971 virtual/blink-cors/http/tests/security/script-crossorigin-redirect-credentials.html [ Failure ]
 crbug.com/905971 [ Win ] virtual/blink-cors/external/wpt/service-workers/service-worker/detached-context.https.html [ Pass Crash ]
+
+# Sheriff 2019-06-04
+crbug.com/970135 [ Mac ] virtual/focusless-spat-nav/fast/spatial-navigation/focusless/snav-focusless-interested-element-indicated.html [ Failure ]