chore(package): update sinon to version 8.0.0

Author: greenkeeper[bot]

package.json

@@ -46,7 +46,7 @@
     "postcss-simple-vars": "^5.0.0",
     "proxyquire": "^2.0.0",
     "semantic-release": "^15.0.0",
-    "sinon": "^7.1.1",
+    "sinon": "^8.0.0",
     "tempy": "^0.3.0",
     "xo": "^0.25.3"
   },