[Sheriff] Disable ContextMenuTestCase/testContextMenu

TBR=rohitrao@chromium.org
Bug: 1084280

Change-Id: I220f5ba04f8c974947764cdb883a9f78af14cd57
Reviewed-on: https://chromium-review.googlesource.com/c/chromium/src/+/2218613Reviewed-by: Leonard Grey <lgrey@chromium.org>
Commit-Queue: Leonard Grey <lgrey@chromium.org>
Cr-Commit-Position: refs/heads/master@{#772349}

ios/web/shell/test/context_menu_egtest.mm

@@ -48,7 +48,7 @@ const char kHtmlFile[] =
 }
 
 // Tests context menu appears on a regular link.
-- (void)testContextMenu {
+- (void)DISABLED_testContextMenu {
   const char linkID[] = "normal-link";
   NSString* const linkText = @"normal-link-text";
   const GURL pageURL = _server.GetURL(kHtmlFile);