fix typo in migration script

Change-Id: Idad10e62eaf5c12aaff74095233d1a93af586bbb
Reviewed-on: https://gerrit.instructure.com/2789
Tested-by: Hudson <hudson@instructure.com>
Reviewed-by: JT Olds <jt@instructure.com>

db/migrate/20110302054028_change_fudge_points_to_float.rb

@@ -4,6 +4,6 @@ class ChangeFudgePointsToFloat < ActiveRecord::Migration
   end
 
   def self.down
-    change_column :quiz_submission, :fudge_points, :integer
+    change_column :quiz_submissions, :fudge_points, :integer
   end
 end