Update GitHub Actions workflows. (#773)

This PR was triggered by @t0yv0 generated by the
update-workflows-ecosystem-providers workflow in the pulumi/ci-mgmt
repo, from commit
[b8b29dc51d452160accc76a310efd6eb38760b50](b8b29dc51d).

Co-authored-by: Pulumi Bot <bot@pulumi.com>

.github/workflows/weekly-pulumi-update.yml

@@ -109,9 +109,7 @@ jobs:
 
         msg="Automated upgrade: bump pulumi/pulumi to ${ver}"
 
-        # See https://github.com/cli/cli/issues/6485#issuecomment-2560935183 for --head workaround
-
-        gh pr create -t "$msg" -b "$msg" --head "$(git branch --show-current)"
+        gh pr create -t "$msg" -b "$msg"
       env:
         GITHUB_TOKEN: ${{ steps.esc-secrets.outputs.PULUMI_BOT_TOKEN }}
     name: weekly-pulumi-update