chore(deps): update dependency nyc to v15

Author: renovate-bot

Diff for: package.json

@@ -56,7 +56,7 @@
     "cz-conventional-changelog": "3.0.2",
     "diff": "4.0.1",
     "execa": "4.0.0",
-    "nyc": "14.1.1",
+    "nyc": "15.0.0",
     "prop-types": "15.7.2",
     "react": "16.12.0",
     "rimraf": "3.0.0",