Adapt sync_ui_util.cc override to removal of sync_ui_util namespace

Chromium change:

https://chromium.googlesource.com/chromium/src/+/5cd115f54c670fafd04972a66725113fd51302ba

commit 5cd115f54c670fafd04972a66725113fd51302ba
Author: Victor Hugo Vianna Silva <victorvianna@google.com>
Date:   Mon Jun 14 17:08:28 2021 +0000

    Remove sync_ui_util namespace from c/b/sync/sync_ui_util.h

    No behavior is changed.
    Namespaces are discouraged for top-level embedders [1]. Since the
    namespace is removed:

    1) Rename the following so they aren't too generic:
    - MessageType -> SyncStatusMessageType
    - ActionType -> SyncStatusActionType
    - StatusLabels -> SyncStatusLabels
    - GetStatusLabels() -> GetSyncStatusLabels()
    - GetStatus() -> GetSyncStatus()

    2) Use enum classes rather than raw enums.

    Besides the above:
    3) Convert ENUM_VALUE casing to kEnumValue.
    4) Avoid one line over 80 characters and remove one unused function in
    sync_ui_util_unittest.cc

    [1] https://source.chromium.org/chromium/chromium/src/+/main:styleguide/c++/c++-dos-and-donts.md;l=294;drc=be05130dfdd2db2b14f73d0b99be3a2b4b118869

    Fixed: 1219516

chromium_src/chrome/browser/sync/sync_ui_util.cc

@@ -3,17 +3,13 @@
 // License, v. 2.0. If a copy of the MPL was not distributed with this file,
 // you can obtain one at http://mozilla.org/MPL/2.0/.
 
-#define GetAvatarSyncErrorType GetAvatarSyncErrorType_ChromiumImpl
+#define GetAvatarSyncErrorType GetAvatarSyncErrorType_Unused
 #include "../../../../../chrome/browser/sync/sync_ui_util.cc"
 #undef GetAvatarSyncErrorType
 
-namespace sync_ui_util {
-
 absl::optional<AvatarSyncErrorType> GetAvatarSyncErrorType(Profile* profile) {
   // Brave Sync works differently in that there is no sign-in
   // and nothing to prompt the user to manage once their sync
   // chain is setup.
   return absl::nullopt;
 }
-
-}  // namespace sync_ui_util