Fix express vulnerability (#4076)

frameworks/JavaScript/express/package.json

@@ -13,7 +13,7 @@
     "mongoose": "5.0.6",
     "mysql": "2.16.0",
     "mysql2": "1.6.1",
-    "pg": "4.2.0",
+    "pg": "4.5.7",
     "pg-promise": "8.4.6",
     "pug": "2.0.1",
     "sequelize": "3.30.0"