chore(deps): update dependency nyc to v15

Author: renovate-bot

app/templates/package.json

@@ -29,7 +29,7 @@
     "chance": "1.1.4",
     "husky": "3.1.0",
     "mocha": "6.2.2",
-    "nyc": "14.1.1",
+    "nyc": "15.0.0",
     "proxyquire": "2.1.3",
     "sinon": "7.5.0"
   }