fix(package): update sinon to version 9.0.0

Closes #35

Author: greenkeeper[bot]

package.json

@@ -36,7 +36,7 @@
     "@types/sinon-chai": "^3.2.3",
     "chai": "^4.2.0",
     "mocha": "^6.2.2",
-    "sinon": "^7.5.0",
+    "sinon": "^9.0.0",
     "sinon-chai": "^3.3.0"
   },
   "devDependencies": {