Bump knapsack_pro from 8.3.0 to 8.4.0

Bumps [knapsack_pro](https://github.com/KnapsackPro/knapsack_pro-ruby) from 8.3.0 to 8.4.0.
- [Changelog](https://github.com/KnapsackPro/knapsack_pro-ruby/blob/main/CHANGELOG.md)
- [Commits](https://github.com/KnapsackPro/knapsack_pro-ruby/compare/v8.3.0...v8.4.0)

---
updated-dependencies:
- dependency-name: knapsack_pro
  dependency-version: 8.4.0
  dependency-type: direct:development
  update-type: version-update:semver-minor
...

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

Gemfile

@@ -71,7 +71,7 @@ group :development, :test do
   gem "factory_bot_rails", "~> 6.5.1"
   gem "faker", "~> 3.5.2"
   gem "i18n-tasks", "~> 0.9.37"
-  gem "knapsack_pro", "~> 8.3.0"
+  gem "knapsack_pro", "~> 8.4.0"
   gem "launchy", "~> 3.1.1"
   gem "letter_opener_web", "~> 3.0.0"
 end