Update sync-dev-to-vX.Y-dev-experiment.yaml

Author: ralfhandl

.github/workflows/sync-dev-to-vX.Y-dev-experiment.yaml

@@ -46,7 +46,7 @@ jobs:
               --label "Housekeeping" \
               --title "$BASE: update from $HEAD" \
               --body "Merge \`$HEAD\` into \`$BASE\`.")
-            gh pr merge $PR --merge --auto
+            gh pr merge $PR --merge --admin
           done
         env:
           GH_TOKEN: ${{ steps.generate-token.outputs.token }}