Silence deprecation warning in test

Missed a case that only occured for mysql/mysql2

activerecord/test/cases/migration_test.rb

@@ -12,6 +12,9 @@
 require MIGRATIONS_ROOT + "/decimal/1_give_me_big_numbers"
 
 class BigNumber < ActiveRecord::Base
+  unless current_adapter?(:PostgreSQLAdapter, :SQLite3Adapter)
+    property :value_of_e, Type::Integer.new
+  end
   property :world_population, Type::Integer.new
   property :my_house_population, Type::Integer.new
 end