Update mocha requirement from ~> 2.1.0 to ~> 2.2.0 (#292)

Updates the requirements on [mocha](https://github.com/freerange/mocha) to permit the latest version.
- [Changelog](https://github.com/freerange/mocha/blob/main/RELEASE.md)
- [Commits](freerange/mocha@v2.1.0...v2.2.0)

---
updated-dependencies:
- dependency-name: mocha
  dependency-type: direct:production
...

Signed-off-by: dependabot[bot] <support@github.com>
Co-authored-by: dependabot[bot] <49699333+dependabot[bot]@users.noreply.github.com>

Gemfile

@@ -9,6 +9,6 @@ gem "rake"
 gem "memory_profiler", require: false
 gem "minitest"
 gem "minitest-reporters"
-gem "mocha", "~> 2.1.0"
+gem "mocha", "~> 2.2.0"
 gem "rubocop", require: false
 gem "yard"