chore(package): update supertest to version 4.0.0

Author: greenkeeper[bot]

package.json

@@ -69,7 +69,7 @@
         "copy-webpack-plugin": "^4.5.2",
         "glob": "^7.1.2",
         "mocha": "^6.0.0",
-        "supertest": "^3.1.0",
+        "supertest": "^4.0.0",
         "ts-loader": "^4.4.2",
         "typescript": "^3.0.1",
         "uglifyjs-webpack-plugin": "^2.0.0",