Add app_launch_predictor_test_util.h to test BUILD.gn

This header appears never to have been listed in chrome/test/BUILD.gn,
and deleting some files that referenced it caused compile failures.
Let's add it to the build file in case this causes further issues.

Bug: 1065406
Change-Id: If550192a6f8601560f176b23dc8832d843cab2f8
Reviewed-on: https://chromium-review.googlesource.com/c/chromium/src/+/2124341
Commit-Queue: Tony Yeoman <tby@chromium.org>
Reviewed-by: Xiyuan Xia <xiyuan@chromium.org>
Cr-Commit-Position: refs/heads/master@{#755221}

chrome/test/BUILD.gn

@@ -4377,6 +4377,7 @@ test("unit_tests") {
       "../browser/ui/app_list/search/cros_action_history/cros_action_recorder_unittest.cc",
       "../browser/ui/app_list/search/launcher_search/launcher_search_icon_image_loader_unittest.cc",
       "../browser/ui/app_list/search/search_result_ranker/app_launch_event_logger_unittest.cc",
+      "../browser/ui/app_list/search/search_result_ranker/app_launch_predictor_test_util.h",
       "../browser/ui/app_list/search/search_result_ranker/app_launch_predictor_unittest.cc",
       "../browser/ui/app_list/search/search_result_ranker/app_list_launch_metrics_provider_unittest.cc",
       "../browser/ui/app_list/search/search_result_ranker/app_search_result_ranker_unittest.cc",
@@ -4434,6 +4435,8 @@ test("unit_tests") {
       "//ash/strings",
       "//chrome/browser/chromeos:test_support",
       "//chrome/browser/resources/chromeos/zip_archiver/cpp:ziparchiver_unittests",
+      "//chrome/browser/ui/app_list/search/search_result_ranker:app_launch_predictor_proto",
+      "//chrome/browser/ui/app_list/search/search_result_ranker:recurrence_ranker_proto",
       "//chromeos/services/machine_learning/public/cpp:test_support",
       "//components/arc:arc_test_support",
     ]