No mb_chars needed anymore

lib/gitlab/ldap/user.rb

@@ -14,7 +14,7 @@ module Gitlab
           # LDAP distinguished name is case-insensitive
           identity = ::Identity.
             where(provider: provider).
-            iwhere(extern_uid: uid.mb_chars.to_s).last
+            iwhere(extern_uid: uid).last
           identity && identity.user
         end
       end