Fix redundant parameter to removeColumn in db migration scripts

Author: jackycute

lib/migrations/20161009040430-support-delete-note.js

@@ -6,6 +6,6 @@ module.exports = {
   },
 
   down: function (queryInterface, Sequelize) {
-    queryInterface.removeColumn('Notes', 'deletedAt', Sequelize.DATE);
+    queryInterface.removeColumn('Notes', 'deletedAt');
   }
 };

lib/migrations/20161201050312-support-email-signin.js

@@ -7,7 +7,7 @@ module.exports = {
   },
 
   down: function (queryInterface, Sequelize) {
-    queryInterface.removeColumn('Users', 'email', Sequelize.TEXT);
-    queryInterface.removeColumn('Users', 'password', Sequelize.TEXT);
+    queryInterface.removeColumn('Users', 'email');
+    queryInterface.removeColumn('Users', 'password');
   }
 };