Update rubocop-performance requirement from ~> 1.20.1 to ~> 1.21.1

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@v1.20.1...v1.21.1)

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

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

Author: dependabot[bot]

publify_textfilter_code.gemspec

@@ -24,7 +24,7 @@ Gem::Specification.new do |s|
 
   s.add_development_dependency "rspec-rails", "~> 6.0"
   s.add_development_dependency "rubocop", "~> 1.63.1"
-  s.add_development_dependency "rubocop-performance", "~> 1.20.1"
+  s.add_development_dependency "rubocop-performance", "~> 1.21.1"
   s.add_development_dependency "rubocop-rails", "~> 2.25.0"
   s.add_development_dependency "rubocop-rspec", "~> 2.26.0"
   s.add_development_dependency "simplecov", "~> 0.22.0"