Update dependency supertest to v6.1.3

Author: renovate-bot

experiments/guess-static-sites/package-lock.json

@@ -31,6 +31,6 @@
     "path": "0.12.7",
     "puppeteer": "7.0.4",
     "standard": "16.0.3",
-    "supertest": "6.0.1"
+    "supertest": "6.1.3"
   }
 }