chore(deps): update dependency tslint to v5.20.0

Author: renovate-bot

frontend/package.json

@@ -63,7 +63,7 @@
     "karma-jasmine-html-reporter": "1.4.2",
     "protractor": "5.4.2",
     "ts-node": "8.3.0",
-    "tslint": "5.18.0",
+    "tslint": "5.20.0",
     "typescript": "3.4.5"
   }
 }