Bump the rubocop-dependencies group with 1 update

Updates the requirements on [rubocop-performance](https://github.com/rubocop/rubocop-performance) to permit the latest version.

Updates `rubocop-performance` to 1.21.0
- [Release notes](https://github.com/rubocop/rubocop-performance/releases)
- [Changelog](https://github.com/rubocop/rubocop-performance/blob/master/CHANGELOG.md)
- [Commits](rubocop/rubocop-performance@v1.20.2...v1.21.0)

---
updated-dependencies:
- dependency-name: rubocop-performance
  dependency-type: direct:development
  dependency-group: rubocop-dependencies
...

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

Gemfile

@@ -16,7 +16,7 @@ group(:development) do
   gem('benchmark-ips', '~> 2.13.0', require: false)
   gem('rubocop', '~> 1.62.1', require: false)
   gem('rubocop-rake', '~> 0.6.0', require: false)
-  gem('rubocop-performance', '~> 1.20.2', require: false)
+  gem('rubocop-performance', '~> 1.21.0', require: false)
   gem('rubocop-thread_safety', '~> 0.5.1', require: false)
 end