Bump nyc from 10.3.2 to 15.0.1

Bumps [nyc](https://github.com/istanbuljs/nyc) from 10.3.2 to 15.0.1.
- [Release notes](https://github.com/istanbuljs/nyc/releases)
- [Changelog](https://github.com/istanbuljs/nyc/blob/master/CHANGELOG.md)
- [Commits](istanbuljs/nyc@v10.3.2...v15.0.1)

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

package.json

@@ -41,7 +41,7 @@
     "eslint-plugin-promise": "^3.4.0",
     "eslint-plugin-standard": "^3.0.1",
     "koa": "^1.7.0",
-    "nyc": "^10.0.0",
+    "nyc": "^15.0.1",
     "tunnel-agent": "^0.6.0"
   }
 }