Update webpack-dev-server 3.1.5 → 3.1.7 (#4955)

This fixes the functionality of this dependency for Node 10 and above.

Refs: webpack/webpack-dev-server#1451
Refs: nodejs/node#21665

Author: addaleax

Diff for: package.json

@@ -68,7 +68,7 @@
     "uglifyjs-webpack-plugin": "1.2.5",
     "url-loader": "1.0.1",
     "webpack": "4.8.3",
-    "webpack-dev-server": "3.1.5",
+    "webpack-dev-server": "3.1.7",
     "webpack-manifest-plugin": "2.0.3",
     "whatwg-fetch": "2.0.4"
   },