Sheriff: Mark fast/forms/select/disabled-select-change-index.html on mac bots

Bug: 987108
Change-Id: I7a1c2b89a0ed6cfce4d2b9761b0928a1808ebf39
Notry: true
Tbr: nhiroki@chromium.org
Reviewed-on: https://chromium-review.googlesource.com/c/chromium/src/+/1715888Reviewed-by: Hiroki Nakagawa <nhiroki@chromium.org>
Commit-Queue: Hiroki Nakagawa <nhiroki@chromium.org>
Cr-Commit-Position: refs/heads/master@{#680275}

third_party/blink/web_tests/TestExpectations

@@ -6351,3 +6351,4 @@ crbug.com/986666 virtual/disable-blink-gen-property-trees/animations/web-animati
 crbug.com/986019 animations/play-state.html [ Pass Timeout ]
 crbug.com/986019 virtual/threaded/animations/play-state.html [ Pass Timeout ]
 crbug.com/986019 virtual/disable-blink-gen-property-trees/animations/play-state.html [ Pass Timeout ]
+crbug.com/987108 [ Mac ] fast/forms/select/disabled-select-change-index.html [ Failure ]