Update test-dup.yaml

Author: b-rodrigues

.github/workflows/test-dup.yaml

@@ -44,5 +44,11 @@ jobs:
       - name: Remove lines starting with `#` from generated expression
         run: sed -i '/^#/d' default.nix
 
+      - name: Check out default.nix
+        run: cat default.nix
+
+      - name: Check out test default.nix with dups
+        run: cat mlr3_dups_default.nix
+
       - name: Compare lines and fail if different
         run: diff -q default.nix mlr3_dups_default.nix || exit 1