Update update-changelog.yml

Author: bastianschwarz

.github/workflows/update-changelog.yml

@@ -35,7 +35,7 @@ jobs:
         with:
           token: ${{ secrets.GITHUB_TOKEN }}
           exclude_labels: ${{inputs.exclude-labels}}
-          future_release: ${{inputs.future-release}}
+          future_release: ${{ format('{0}', inputs.future-release) }} 
           release_branch: ${{inputs.release-branch}}
 
       - name: commit updated changelog