Bump mocha from 6.2.3 to 8.2.1

Bumps [mocha](https://github.com/mochajs/mocha) from 6.2.3 to 8.2.1.
- [Release notes](https://github.com/mochajs/mocha/releases)
- [Changelog](https://github.com/mochajs/mocha/blob/master/CHANGELOG.md)
- [Commits](mochajs/mocha@v6.2.3...v8.2.1)

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

package.json

@@ -37,7 +37,7 @@
     "eslint": "^6.8.0",
     "eslint-config-hexo": "^4.1.0",
     "hexo": "^3.9.0",
-    "mocha": "^6.2.2",
+    "mocha": "^8.2.1",
     "nyc": "^15.0.0"
   },
   "files": [