build(deps-dev): bump mocha from 2.7.1 to 3.1.0

Bumps [mocha](https://github.com/freerange/mocha) from 2.7.1 to 3.1.0.
- [Changelog](https://github.com/freerange/mocha/blob/main/RELEASE.md)
- [Commits](https://github.com/freerange/mocha/compare/v2.7.1...v3.1.0)

---
updated-dependencies:
- dependency-name: mocha
  dependency-version: 3.1.0
  dependency-type: direct:development
  update-type: version-update:semver-major
...

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

Gemfile.lock

@@ -222,7 +222,7 @@ GEM
       logger
     mini_mime (1.1.5)
     minitest (5.26.2)
-    mocha (2.7.1)
+    mocha (3.1.0)
       ruby2_keywords (>= 0.0.5)
     mono_logger (1.1.2)
     multi_json (1.17.0)