updated user store to use user service for user update operation. added revision date updates to user service update method.

src/Core/Services/UserService.cs

@@ -70,6 +70,7 @@ namespace Bit.Core.Services
                 throw new ApplicationException("Use register method to create a new user.");
             }
 
+            user.RevisionDate = DateTime.UtcNow;
             await _userRepository.ReplaceAsync(user);
         }