Update debug requirement from ~> 1.9.0 to ~> 1.9.1 (#242)

Updates the requirements on [debug](https://github.com/ruby/debug) to permit the latest version.
- [Release notes](https://github.com/ruby/debug/releases)
- [Commits](ruby/debug@v1.9.0...v1.9.1)

---
updated-dependencies:
- dependency-name: debug
  dependency-type: direct:development
...

Signed-off-by: dependabot[bot] <[email protected]>
Co-authored-by: dependabot[bot] <49699333+dependabot[bot]@users.noreply.github.com>

Gemfile

@@ -12,7 +12,7 @@ group(:development, :test) do
 end
 
 group(:development) do
-  gem('debug', '~> 1.9.0', require: false)
+  gem('debug', '~> 1.9.1', require: false)
   gem('yard', '~> 0.9.34', require: false)
   gem('benchmark-ips', '~> 2.13.0', require: false)
   gem('rubocop', '~> 1.59.0', require: false)