Use pull request for Homebrew tap formula updates

The homebrew-tap repository requires verified commit signatures
via org-level rulesets, which cannot be excluded per-repo.
Switch to creating a PR instead of pushing directly.

Signed-off-by: Bryan Frimin <bryan@getprobo.com>

.goreleaser.yaml

@@ -157,6 +157,8 @@ brews:
       owner: getprobo
       name: homebrew-tap
       token: "{{ .Env.HOMEBREW_TAP_GITHUB_TOKEN }}"
+      pull_request:
+        enabled: true
     commit_author:
       name: probo-bot
       email: bot@getprobo.com