Add Ruby version: 4.0.6

[rails-bot]

🤖 Automated Ruby Version Update

This PR adds 1 new Ruby version(s) detected from rbenv/ruby-build:

• 4.0.6

Changes Made

• .github/ruby-versions.json
• features/src/ruby/devcontainer-feature.json
• features/src/ruby/README.md
• features/test/ruby/test.sh
• features/test/ruby/with_rbenv.sh
• features/test/ruby/with_precompiled_rubies.sh

Details

• Updated Ruby version matrix in .github/ruby-versions.json
• Updated default Ruby version in features/src/ruby/devcontainer-feature.json (if applicable)
• Updated documentation in features/src/ruby/README.md (if applicable)
• Updated test files to use new default version (if applicable)
• Bumped feature version (if default Ruby version changed)

Next Steps

After this PR is merged:

1. Feature will be published automatically if version was bumped
2. Images will be built and published (requires approval)
3. GitHub releases will be created

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This PR was created automatically by the Ruby version checker script.

Run: https://github.com/rails/devcontainer/actions/runs/29303366712