Update rubocop requirement from ~> 1.75.6 to ~> 1.78.0

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@v1.75.6...v1.78.0)

---
updated-dependencies:
- dependency-name: rubocop
  dependency-version: 1.78.0
  dependency-type: direct:development
...

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

Author: dependabot[bot]

publify_core.gemspec

@@ -58,7 +58,7 @@ Gem::Specification.new do |s|
   s.add_development_dependency "rails-controller-testing", "~> 1.0.1"
   s.add_development_dependency "rake-manifest", "~> 0.2.0"
   s.add_development_dependency "rspec-rails", "~> 6.0"
-  s.add_development_dependency "rubocop", "~> 1.75.6"
+  s.add_development_dependency "rubocop", "~> 1.78.0"
   s.add_development_dependency "rubocop-capybara", "~> 2.22.1"
   s.add_development_dependency "rubocop-factory_bot", "~> 2.27.1"
   s.add_development_dependency "rubocop-performance", "~> 1.25.0"