chore(package): update nyc to version 6.6.0

https://greenkeeper.io/

Author: greenkeeperio-bot

package.json

@@ -34,7 +34,7 @@
   },
   "devDependencies": {
     "ava": "^0.13.0",
-    "nyc": "^6.0.0",
+    "nyc": "^6.6.0",
     "snyk": "^1.13.1"
   }
 }