fix a broken test

The commit 2f632f5391 extracted the
options into constants and while doing so, there was a minor error of
using a wrong constant name.

railties/lib/rails/generators/generated_attribute.rb

@@ -18,7 +18,7 @@ module Rails
           # if user provided "name:index" instead of "name:string:index"
           # type should be set blank so GeneratedAttribute's constructor
           # could set it to :string
-          has_index, type = type, nil if UNIQ_INDEX_OPTIONS.include?(type)
+          has_index, type = type, nil if INDEX_OPTIONS.include?(type)
 
           type, attr_options = *parse_type_and_options(type)
           new(name, type, has_index, attr_options)