Update rubocop requirement from ~> 1.80.0 to ~> 1.81.6

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@v1.80.0...v1.81.6)

---
updated-dependencies:
- dependency-name: rubocop
  dependency-version: 1.81.6
  dependency-type: direct:development
...

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

Author: dependabot[bot]

Gemfile

@@ -53,7 +53,7 @@ group(:test) do
   gem 'webrick', '~> 1.7', require: false
   gem 'yard', require: false
 
-  gem 'rubocop', '~> 1.80.0', require: false, platforms: [:ruby]
+  gem 'rubocop', '~> 1.81.6', require: false, platforms: [:ruby]
   gem 'rubocop-i18n', '~> 3.0', require: false, platforms: [:ruby]
   gem 'rubocop-performance', '~> 1.0', require: false, platforms: [:ruby]
   gem 'rubocop-rake', '~> 0.6', require: false, platforms: [:ruby]