Migrate `brews` section to `homebrew_casks` in .goreleaser.yaml

[masutaka]

🔗 https://github.com/masutaka/github-nippou/actions/runs/17696543005/job/50296762253

brews is being phased out in favor of homebrew_casks, check https://goreleaser.com/deprecations#brews for more info

Warning

install and test doesn't exist in homebrew_casks.