Update rubocop-rspec requirement from ~> 3.7.0 to ~> 3.8.0

Updates the requirements on [rubocop-rspec](https://github.com/rubocop/rubocop-rspec) to permit the latest version.
- [Release notes](https://github.com/rubocop/rubocop-rspec/releases)
- [Changelog](https://github.com/rubocop/rubocop-rspec/blob/master/CHANGELOG.md)
- [Commits](rubocop/rubocop-rspec@v3.7.0...v3.8.0)

---
updated-dependencies:
- dependency-name: rubocop-rspec
  dependency-version: 3.8.0
  dependency-type: direct:development
...

Signed-off-by: dependabot[bot] <[email protected]>

Author: dependabot[bot]

Gemfile

@@ -10,5 +10,5 @@ group :development do
   gem 'rubocop', '~> 1.81.0'
   gem 'rubocop-performance', '~> 1.26.0'
   gem 'rubocop-rake', '~> 0.7.1'
-  gem 'rubocop-rspec', '~> 3.7.0'
+  gem 'rubocop-rspec', '~> 3.8.0'
 end