move sync_promo_ui to non-webui-specific directory

chrome/browser/signin/DEPS

 include_rules = [
   # Sign-in logic is being componentized (moved to //components, where
   # it won't depend back on //chrome), so we have restrictive DEPS and
   # are trying to get the list of temporarily-allowed (!-prefixed
   # rules) below to zero.
   "-chrome/common",
   "-chrome/browser",
   "+chrome/browser/signin",
 
   # TODO(joi): Get this list to zero.
@@ skipping 30 matching lines @@
 ]
 
 specific_include_rules = {
   r".*_[a-z]*test\.cc": [
     # TODO(joi): Get this list to zero.
     "!chrome/browser/browser_process.h",
     "!chrome/browser/prefs/browser_prefs.h",
     "!chrome/browser/sync/profile_sync_service_mock.h",
     "!chrome/browser/ui/browser.h",
     "!chrome/browser/ui/singleton_tabs.h",
+    "!chrome/browser/ui/sync/sync_promo_ui.h",
     "!chrome/browser/ui/tabs/tab_strip_model.h",
-    "!chrome/browser/ui/webui/sync_promo/sync_promo_ui.h",
   ],
 
   # These files are staying in //chrome so no need to limit.
   r"(chrome_signin_manager_delegate|"
   r"signin_names_io_thread.*|"
   r"signin_manager_factory)"
   r"\.(h|cc)": [
     "+chrome/browser",
     "+chrome/common",
   ],
 }