Update register_coauthor.rb

Author: lmrodriguezr

app/models/register_coauthor.rb

@@ -25,7 +25,7 @@ def move_up
     return if order <= 1
 
     register
-      .register_coauthor.where(order: order - 1)
+      .register_coauthors.where(order: order - 1)
       .update(order: order) && update(order: order - 1)
   end