Update warning requirement from ~> 1.4.0 to ~> 1.5.0 (#291)

Updates the requirements on [warning](https://github.com/jeremyevans/ruby-warning) to permit the latest version.
- [Changelog](https://github.com/jeremyevans/ruby-warning/blob/master/CHANGELOG)
- [Commits](jeremyevans/ruby-warning@1.4.0...1.5.0)

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

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

Gemfile

@@ -14,7 +14,7 @@ end
 group :test do
   gem 'test-unit', '~> 3.6.7'
   gem 'test-unit-ruby-core', '~> 1.0'
-  gem 'warning', '~> 1.4.0'
+  gem 'warning', '~> 1.5.0'
 
   gem 'irb', '1.14.2'
   gem 'power_assert', '2.0.4'