Remove unused contentType middleware

src/middleware/contentType.js

@@ -1,8 +0,0 @@
-'use strict';
-
-module.exports = function contentType(type) {
-    return function (req, res, next) {
-        res.setHeader('Content-Type', type);
-        next();
-    };
-};

src/middleware/index.js

@@ -1,7 +1,6 @@
 'use strict';
 
 exports = module.exports = {
-    contentType: require('./contentType'),
     cookieParser: require('cookie-parser'),
     cors: require('./cors'),
     csrf: require('csurf'),