Update CHANGELOG.md

[egmsystems]

532 Added after displayValidationErrors: return ExitCode::USAGE (egmsystems)

Q	A
Is bugfix?	❌
New feature?	✔️
Breaks BC?	✔️/❌
Fixed issues	#532

[what-the-diff[bot]]

PR Summary

• Added return exit code after displaying validation errors This improvement makes sure the program exits gracefully after showing validation errors to users, ensuring a better user experience.

[rob006]

Please add this to original PR (in https://github.com/egmsystems/yii2-gii/tree/patch-4 branch).

[samdark]

I've merged it as is. Next time instead of creating a second branch and pull request for another change, push to the same branch.