Update rubocop requirement from 0.79.0 to 0.80.0 (#169)

Updates the requirements on [rubocop](https://github.com/rubocop-hq/rubocop) to permit the latest version.
- [Release notes](https://github.com/rubocop-hq/rubocop/releases)
- [Changelog](https://github.com/rubocop-hq/rubocop/blob/master/CHANGELOG.md)
- [Commits](rubocop/rubocop@v0.79.0...v0.80.0)

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

Gemfile

@@ -11,5 +11,5 @@ gem "memory_profiler", require: false
 gem "minitest"
 gem "minitest-reporters"
 gem "mocha"
-gem "rubocop", "0.79.0", require: false
+gem "rubocop", "0.80.0", require: false
 gem "yard"