ci: fix auto-publish workflow

Signed-off-by: David Karlsson <david.karlsson@docker.com>

.github/workflows/merge.yml

@@ -13,11 +13,17 @@ jobs:
     if: github.repository_owner == 'docker'
     steps:
       - uses: actions/checkout@v3
+        with:
+          ref: published
+      - name: Reset published branch
+        run: |
+          git fetch origin main:main
+          git reset --hard main
       - name: Create Pull Request
         uses: peter-evans/create-pull-request@5b4a9f6a9e2af26e5f02351490b90d01eb8ec1e5
         with:
           delete-branch: false
-          branch: published
+          branch: published-update
           commit-message: publish updates from main
           labels: area/release
           title: publish updates from main