ci: allow prerelease with empty changelog on deletion

Author: paolobrasolin

.github/workflows/release.yml

@@ -67,6 +67,7 @@ jobs:
           GITHUB_TOKEN: ${{ secrets.GITHUB_TOKEN }}
           UNRELEASED: "delete"
           UNRELEASED_TAG: unreleased
+          ALLOW_EMPTY_CHANGELOG: true
         with:
           args: |
             string-diagrams-${{ steps.labeller.outputs.version }}.tar.gz