homebrew_casks hook emits Homebrew deprecated postflight stanza

Homebrew deprecated the postflight stanza that GoReleaser emits for homebrew_casks[].hooks.post.install. Every brew command that loads openstatushq/homebrew-cli/openstatus now prints:

Warning: Calling `postflight` is deprecated! Use `postflight_steps` instead.
Please report this issue to the openstatushq/homebrew-cli tap (not Homebrew/* repositories), or even better, submit a PR to fix it:
  /opt/homebrew/Library/Taps/openstatushq/homebrew-cli/Casks/openstatus.rb:37

The generated cask is produced from this repo's .goreleaser.yaml:

homebrew_casks:
  - hooks:
      post:
        install: |
          if system_command("/usr/bin/xattr", args: ["-h"]).exit_status == 0
            system_command "/usr/bin/xattr", args: ["-dr", "com.apple.quarantine", "#{staged_path}/openstatus"]
          end

GoReleaser wraps that body in postflight do, and postflight_steps is not a rename of the same Ruby DSL. A tap-only edit will be overwritten on the next release.

Once goreleaser/goreleaser#6873 ships (milestone v2.19.0), this config should become something like:

hooks:
  post:
    install_steps: |
      on_macos do
        run "/usr/bin/xattr", args: ["-dr", "com.apple.quarantine", "{{ .StagedPath }}/openstatus"], must_succeed: false
      end

I reported this on the tap as well. Related: goreleaser/goreleaser#6870, terraform-linters/tflint#2643.

Start in .goreleaser.yaml and review the homebrew_casks hooks.post.install configuration alongside GoReleaser PR #6873 and its v2.19.0 milestone. After the supported syntax is available, verify that generated casks use the replacement install-step form and no longer emit the deprecated postflight stanza or Homebrew warning.