chore(package): update sinon to version 6.0.0

Author: greenkeeper[bot]

package.json

@@ -44,7 +44,7 @@
     "nyc": "^12.0.1",
     "p-retry": "^2.0.0",
     "semantic-release": "^15.0.0",
-    "sinon": "^5.0.0",
+    "sinon": "^6.0.0",
     "tempy": "^0.2.1",
     "xo": "^0.21.0"
   },