[Sync] Fix namespaces for the sync_sessions component.

components/sync_sessions/revisit/bookmarks_page_revisit_observer.h

Index: components/sync_sessions/revisit/bookmarks_page_revisit_observer.h
diff --git a/components/sync_sessions/revisit/bookmarks_page_revisit_observer.h b/components/sync_sessions/revisit/bookmarks_page_revisit_observer.h
index 6953755030f065341b19712cf9d159ce85022216..5ae4bba00d81b5249e0b5fa1e11ae3f587cdccf8 100644
--- a/components/sync_sessions/revisit/bookmarks_page_revisit_observer.h
+++ b/components/sync_sessions/revisit/bookmarks_page_revisit_observer.h
@@ -37,7 +37,7 @@ class BookmarksByUrlProvider {
 // processing in task/thread, which is okay since it only accesses values in
 // memory. Potential slow downs could occur when it fails to get bookmarks lock
 // and when the number of matching Bookmarks for a single URL is very large.
-class BookmarksPageRevisitObserver : public sync_sessions::PageVisitObserver {
+class BookmarksPageRevisitObserver : public PageVisitObserver {
  public:
   explicit BookmarksPageRevisitObserver(
       std::unique_ptr<BookmarksByUrlProvider> provider);