Update dependency @types/node to v11.15.20

Author: renovate-bot

package.json

@@ -31,7 +31,7 @@
   "license": "MIT",
   "devDependencies": {
     "@types/jasmine": "3.5.10",
-    "@types/node": "11.15.12",
+    "@types/node": "11.15.20",
     "jasmine": "3.6.1",
     "jasmine-node": "3.0.0",
     "ts-node": "8.10.1",