loopback#context: fix missing "g" symbol

Author: bajtos

server/middleware/context.js

@@ -3,6 +3,8 @@
 // This file is licensed under the MIT License.
 // License text available at https://opensource.org/licenses/MIT
 
+var g = require('strong-globalize')();
+
 module.exports = function() {
   throw new Error(g.f(
     '%s middleware was removed in version 3.0. See %s for more details.',