Update dependency express to ^4.20.0

Author: mend-for-g.yxqyang.asia[bot]

package.json

@@ -13,7 +13,7 @@
   "dependencies": {
     "async": "^2.6.0",
     "ejs": "^2.5.6",
-    "express": "^4.15.2",
+    "express": "^4.20.0",
     "express-session": "^1.15.6",
     "request-promise": "^4.2.2"
   },