Sheriff: Disable flaky ExtensionWebRequestApiAuthRequiredTest.WebRequestAuthRequiredAsync test

TBR=karandeepb@chromium.org

Bug: 1003598
Change-Id: I3e6afa685223ea09caa8e261ecf9e15773d898b3
Reviewed-on: https://chromium-review.googlesource.com/c/chromium/src/+/1808281Reviewed-by: Fergus Dall <sidereal@google.com>
Cr-Commit-Position: refs/heads/master@{#697009}

chrome/browser/extensions/api/web_request/web_request_apitest.cc

@@ -481,8 +481,9 @@ IN_PROC_BROWSER_TEST_P(ExtensionWebRequestApiAuthRequiredTest,
       << message_;
 }
 
+// TODO(https://crbug.com/1003598): Flake on multiple platforms.
 IN_PROC_BROWSER_TEST_P(ExtensionWebRequestApiAuthRequiredTest,
-                       WebRequestAuthRequiredAsync) {
+                       DISABLED_WebRequestAuthRequiredAsync) {
   CancelLoginDialog login_dialog_helper;
 
   ASSERT_TRUE(StartEmbeddedTestServer());