goreleaser: emit non-deprecated depends_on macos: form

[tariqwest]

Summary

The Homebrew formula generated by this project's GoReleaser config (.goreleaser.yml → brews → custom_block) emits a deprecation warning on every brew invocation against cirruslabs/homebrew-cli:

Warning: Calling `depends_on :macos` with `depends_on macos:` is deprecated! Use `depends_on :macos` with `depends_on macos:` inside an `on_macos` block instead.
Please report this issue to the cirruslabs/homebrew-cli tap (not Homebrew/* repositories), or even better, submit a PR to fix it:
  /opt/homebrew/Library/Taps/cirruslabs/homebrew-cli/softnet.rb:18

The cause is the legacy hash-rocket form depends_on :macos => :sequoia that this config injects into the generated softnet.rb. The brew formula header notes # This file was generated by GoReleaser. DO NOT EDIT., so the only correct fix lives here, not in the tap.

Change

Replaces the legacy form with the modern on_macos do ... end block, which is what Homebrew's deprecation message suggests:

custom_block: |
  on_macos do
    depends_on macos: :sequoia
  end

This is semantically equivalent (softnet is already a macOS-only project per its build targets) and produces a generated formula that no longer warns.

Notes

• The brews.repository field still points to cirruslabs/homebrew-cli from the pre-transfer days. That's left untouched by this PR \u2014 separate concern from the deprecation.
• I have a corresponding local edit applied on my machine to confirm the fix silences the warning end-to-end; once this is released the generated tap formula will pick it up automatically.

[wincent]

Duplicate of #169.