Update mocha requirement from ~> 1.1 to ~> 2.0 (#94)

Updates the requirements on [mocha](https://github.com/freerange/mocha) to permit the latest version.
- [Release notes](https://github.com/freerange/mocha/releases)
- [Changelog](https://github.com/freerange/mocha/blob/main/RELEASE.md)
- [Commits](freerange/mocha@v1.1.0...v2.0.0)

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

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

Author: dependabot[bot]

kitchen-pester.gemspec

@@ -18,7 +18,7 @@ Gem::Specification.new do |spec|
 
   spec.add_development_dependency "rake"
   spec.add_development_dependency "minitest",  "~> 5.3", "< 5.16"
-  spec.add_development_dependency "mocha",     "~> 1.1"
+  spec.add_development_dependency "mocha",     "~> 2.0"
 
   spec.add_dependency "test-kitchen", ">= 1.10", "< 5"
 end