Update dependency supertest to v6.3.4

Author: renovate[bot]

package-lock.json

@@ -12,7 +12,7 @@
     "postcss-reporter": "6.0.1",
     "stylelint": "13.13.1",
     "stylelint-config-standard": "22.0.0",
-    "supertest": "6.1.6"
+    "supertest": "6.3.4"
   },
   "scripts": {
     "test": "jest",