chore(deps-dev): bump nyc from 14.1.1 to 15.0.0 (#108)

Bumps [nyc](https://github.com/istanbuljs/nyc) from 14.1.1 to 15.0.0.
- [Release notes](https://github.com/istanbuljs/nyc/releases)
- [Changelog](https://github.com/istanbuljs/nyc/blob/master/CHANGELOG.md)
- [Commits](istanbuljs/nyc@v14.1.1...v15.0.0)

Signed-off-by: dependabot-preview[bot] <support@dependabot.com>

package.json

@@ -45,7 +45,7 @@
     "hexo": "^4.0.0",
     "hexo-fs": "^2.0.0",
     "mocha": "^6.1.4",
-    "nyc": "^14.1.1",
+    "nyc": "^15.0.0",
     "sinon": "^7.3.2",
     "supertest": "^4.0.2",
     "uuid": "^3.3.2"