Bump mocha from 3.5.3 to 6.2.2

Bumps [mocha](https://github.com/mochajs/mocha) from 3.5.3 to 6.2.2.
- [Release notes](https://github.com/mochajs/mocha/releases)
- [Changelog](https://github.com/mochajs/mocha/blob/master/CHANGELOG.md)
- [Commits](mochajs/mocha@v3.5.3...v6.2.2)

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

package.json

@@ -35,7 +35,7 @@
     "coveralls": "^2.13.1",
     "dirty-chai": "^2.0.1",
     "istanbul": "^1.0.0-alpha.2",
-    "mocha": "^3.5.0",
+    "mocha": "^6.2.2",
     "mocha-lcov-reporter": "^1.3.0",
     "nodemon": "^1.11.0",
     "sinon": "^1.17.7",