chore(package): update sinon to version 9.0.2

Closes #45

Author: greenkeeper[bot]

package.json

@@ -37,7 +37,7 @@
     "express": "^4.16.4",
     "mocha": "^6.0.0",
     "nyc": "^13.3.0",
-    "sinon": "^7.2.4",
+    "sinon": "^9.0.2",
     "supertest": "^4.0.0"
   },
   "dependencies": {}