Update irb-power_assert requirement from 0.3.1 to 0.4.0 (#669)

Updates the requirements on [irb-power_assert](https://github.com/kachick/irb-power_assert) to permit the latest version.
- [Release notes](https://github.com/kachick/irb-power_assert/releases)
- [Commits](kachick/irb-power_assert@v0.3.1...v0.4.0)

---
updated-dependencies:
- dependency-name: irb-power_assert
  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', '~> 13.2.1')
   gem('irb', '~> 1.14.3')
-  gem('irb-power_assert', '0.3.1')
+  gem('irb-power_assert', '0.4.0')
   gem('perfect_toml', '~> 0.9.0', require: false)
 end