Update irb requirement from ~> 1.11.2 to ~> 1.12.0 (#271)

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@v1.11.2...v1.12.0)

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

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

Gemfile

@@ -7,7 +7,7 @@ gemspec
 
 group(:development, :test) do
   gem('rake', '~> 13.1.0')
-  gem('irb', '~> 1.11.2')
+  gem('irb', '~> 1.12.0')
   gem('irb-power_assert', '~> 0.2.0')
 end