chore: Update rubocop requirement from 1.87.0 to 1.88.0 (#1114)

Updates the requirements on [rubocop](https://github.com/rubocop/rubocop) to permit the latest version.
- [Release notes](https://github.com/rubocop/rubocop/releases)
- [Changelog](https://github.com/rubocop/rubocop/blob/master/CHANGELOG.md)
- [Commits](rubocop/rubocop@v1.87.0...v1.88.0)

---
updated-dependencies:
- dependency-name: rubocop
  dependency-version: 1.88.0
  dependency-type: direct:production
...

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

Author: dependabot[bot]

Gemfile

@@ -21,5 +21,5 @@ gem 'minitest', '~> 5.0'
 gem 'minitest-reporters', '~> 1.1'
 gem 'pry'
 gem 'rake', '~> 13.0'
-gem 'rubocop', '1.87.0'
+gem 'rubocop', '1.88.0'
 gem 'yard', '~> 0.9.11'