Update irb requirement from ~> 1.8.3 to ~> 1.9.0 (#446)

Updates the requirements on [irb](https://github.com/ruby/irb) to permit the latest version.
- [Release notes](https://github.com/ruby/irb/releases)
- [Commits](ruby/irb@v1.8.3...v1.9.0)

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

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

Gemfile

@@ -6,7 +6,7 @@ gemspec
 
 group(:development, :test) do
   gem('rake', '~> 13.1.0')
-  gem('irb', '~> 1.8.3')
+  gem('irb', '~> 1.9.0')
   gem('irb-power_assert', '0.2.0')
 end