chore(package): update sinon to version 7.2.6

Closes #330

Author: greenkeeper[bot]

package.json

@@ -110,7 +110,7 @@
     "eslint-plugin-react": "^7.10.0",
     "mocha": "^5.2.0",
     "semantic-release": "^15.9.5",
-    "sinon": "^6.1.4",
+    "sinon": "^7.2.6",
     "sinon-chai": "^3.2.0"
   }
 }