Add irb in development to fix bundle console warnings

[ericproulx]

This PR adds the irb gem to the development group in the Gemfile to resolve warnings that occur when running bundle console.

When bundle console is executed without the irb gem explicitly listed in the Gemfile, bundler shows warnings about missing dependencies. Adding irb to the development group ensures a clean console experience for developers.

Changes:

• Added gem 'irb' to the :development group in Gemfile

Testing:

• Verified that bundle console runs without warnings after this change

[grape-bot]

	1 Warning
⚠️	Unless you're refactoring existing code or improving documentation, please update CHANGELOG.md.

Here's an example of a CHANGELOG.md entry:

* [#2590](https://github.com/ruby-grape/grape/pull/2590): Add irb in development to fix bundle console warnings - [@ericproulx](https://github.com/ericproulx).

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