Update dependency pac-proxy-agent to v4

package.json

@@ -39,7 +39,7 @@
     "axios": "^0.19.2",
     "express": "^4.17.1",
     "express-fileupload": "^1.1.9",
-    "pac-proxy-agent": "^3.0.1",
+    "pac-proxy-agent": "^4.0.0",
     "request": "^2.88.0"
   },
   "devDependencies": {