Make the docs reference the correct function. [Tobi Reif]

git-svn-id: http://svn-commit.rubyonrails.org/rails/trunk@8802 5ecf4fe2-1ee6-0310-87b1-e25e094e27de

activerecord/lib/active_record/validations.rb

@@ -610,7 +610,7 @@ def validates_length_of(*attrs)
       #
       # Because this check is performed outside the database there is still a chance that duplicate values
       # will be inserted in two parallel transactions.  To guarantee against this you should create a 
-      # unique index on the field. See +create_index+ for more information.
+      # unique index on the field. See +add_index+ for more information.
       #
       # Configuration options:
       # * <tt>message</tt> - Specifies a custom error message (default is: "has already been taken")