Bump mocha from 6.2.2 to 7.0.0

Bumps [mocha](https://github.com/mochajs/mocha) from 6.2.2 to 7.0.0.
- [Release notes](https://github.com/mochajs/mocha/releases)
- [Changelog](https://github.com/mochajs/mocha/blob/master/CHANGELOG.md)
- [Commits](mochajs/mocha@v6.2.2...v7.0.0)

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

package.json

@@ -29,7 +29,7 @@
     "eslint": "^6.0.1",
     "eslint-config-hexo": "^4.0.0",
     "hexo": "^4.2.0",
-    "mocha": "^6.1.4",
+    "mocha": "^7.0.0",
     "nyc": "^15.0.0"
   },
   "dependencies": {