Remove deprecated extension notification from shortcuts_extensions_manager.h/cc

chrome/browser/BUILD.gn

Index: chrome/browser/BUILD.gn
diff --git a/chrome/browser/BUILD.gn b/chrome/browser/BUILD.gn
index 9c61162e47312ba0939abe66c549c802d72a6ba4..c75bc1d27ad458e15c478599ae51ef39c0253611 100644
--- a/chrome/browser/BUILD.gn
+++ b/chrome/browser/BUILD.gn
@@ -84,8 +84,6 @@ split_static_library("browser") {
     "autocomplete/in_memory_url_index_factory.h",
     "autocomplete/shortcuts_backend_factory.cc",
     "autocomplete/shortcuts_backend_factory.h",
-    "autocomplete/shortcuts_extensions_manager.cc",
-    "autocomplete/shortcuts_extensions_manager.h",
     "autofill/personal_data_manager_factory.cc",
     "autofill/personal_data_manager_factory.h",
     "autofill/risk_util.cc",
@@ -1713,6 +1711,8 @@ split_static_library("browser") {
       "accessibility/animation_policy_prefs.h",
       "autocomplete/keyword_extensions_delegate_impl.cc",
       "autocomplete/keyword_extensions_delegate_impl.h",
+      "autocomplete/shortcuts_extensions_manager.cc",
+      "autocomplete/shortcuts_extensions_manager.h",
       "browsing_data/hosted_apps_counter.cc",
       "browsing_data/hosted_apps_counter.h",
       "content_settings/content_settings_internal_extension_provider.cc",