Revert "removed the non-used label"

This reverts commit 2bccea1b.

lib/csv_generator.rb

@@ -106,7 +106,7 @@ SQL
     #
     #
     sql = <<SQL
-          SELECT '%EMAIL%','%NAME%'
+          SELECT '%EMAIL%','%NAME%','%INVITATION_LINK%'
           UNION
             SELECT `users`.email AS '%EMAIL%',
                    IF( `profiles`.full_name IS NOT NULL AND `profiles`.full_name != "",