Change namespace to ash for //ash/components/settings

Codes in //ash/components/settings are a part of the ash-chrome, so
namespace is changed to ash.

To avoid churn during other namespace transitions in future, this CL has
temporary 'using' declarations.

This CL is part of the Chrome OS source code directory migration:
https://docs.google.com/document/d/1g-98HpzA8XcoGBWUv1gQNr4rbnD5yfvbtYZyPDDbkaE.

Change-Id: I04d46db6fc658f859c527ad337b0c1df6d8eb0ce
Bug: 1164001
Reviewed-on: https://chromium-review.googlesource.com/c/chromium/src/+/3260132
Commit-Queue: Yeunjoo Choi <[email protected]>
Reviewed-by: Hidehiko Abe <[email protected]>
Owners-Override: Hidehiko Abe <[email protected]>
Cr-Commit-Position: refs/heads/main@{#940155}
diff --git a/chrome/browser/ui/webui/help/help_utils_chromeos.cc b/chrome/browser/ui/webui/help/help_utils_chromeos.cc
index 9daf69bf..81003fd 100644
--- a/chrome/browser/ui/webui/help/help_utils_chromeos.cc
+++ b/chrome/browser/ui/webui/help/help_utils_chromeos.cc
@@ -28,7 +28,7 @@
     return default_update_over_cellular_allowed;
 
   const base::Value* types_value =
-      settings->GetPref(chromeos::kAllowedConnectionTypesForUpdate);
+      settings->GetPref(ash::kAllowedConnectionTypesForUpdate);
   if (!types_value)
     return default_update_over_cellular_allowed;
   CHECK(types_value->is_list());