Update rubocop-performance requirement from ~> 1.19.0 to ~> 1.20.0

Updates the requirements on [rubocop-performance](https://github.com/rubocop/rubocop-performance) to permit the latest version.
- [Release notes](https://github.com/rubocop/rubocop-performance/releases)
- [Changelog](https://github.com/rubocop/rubocop-performance/blob/master/CHANGELOG.md)
- [Commits](rubocop/rubocop-performance@v1.19.0...v1.20.0)

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

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

publify_core.gemspec

@@ -60,7 +60,7 @@ Gem::Specification.new do |s|
   s.add_development_dependency "rubocop", "~> 1.59.0"
   s.add_development_dependency "rubocop-capybara", "~> 2.19.0"
   s.add_development_dependency "rubocop-factory_bot", "~> 2.24.0"
-  s.add_development_dependency "rubocop-performance", "~> 1.19.0"
+  s.add_development_dependency "rubocop-performance", "~> 1.20.0"
   s.add_development_dependency "rubocop-rails", "~> 2.23.0"
   s.add_development_dependency "rubocop-rspec", "~> 2.25.0"
   s.add_development_dependency "shoulda-matchers", "~> 5.3"