Remove stale identity_test_utils.h includes

Forgot to do this in the CLs converting away from these utils.

TBR=sdefresne@chromium.org

Bug: 896180
Change-Id: Ifa1766efc5ec91c5313658d65fdfc0fc48bc9fe1
Reviewed-on: https://chromium-review.googlesource.com/c/1288529Reviewed-by: Colin Blundell <blundell@chromium.org>
Commit-Queue: Colin Blundell <blundell@chromium.org>
Cr-Commit-Position: refs/heads/master@{#600695}

chrome/browser/ui/search/search_tab_helper_unittest.cc

@@ -36,7 +36,6 @@
 #include "ipc/ipc_message.h"
 #include "ipc/ipc_test_sink.h"
 #include "net/base/net_errors.h"
-#include "services/identity/public/cpp/identity_test_utils.h"
 #include "testing/gmock/include/gmock/gmock.h"
 #include "testing/gtest/include/gtest/gtest.h"
 #include "ui/base/l10n/l10n_util.h"

chrome/browser/ui/toolbar/media_router_contextual_menu_unittest.cc

@@ -25,7 +25,6 @@
 #include "chrome/grit/generated_resources.h"
 #include "chrome/test/base/browser_with_test_window_test.h"
 #include "services/identity/public/cpp/identity_manager.h"
-#include "services/identity/public/cpp/identity_test_utils.h"
 #include "testing/gmock/include/gmock/gmock.h"
 #include "testing/gtest/include/gtest/gtest.h"
 #include "ui/base/l10n/l10n_util.h"