Apply suggestion from @noonio

Author: noonio

.github/workflows/publish-docs.yaml

@@ -57,7 +57,7 @@ mkdir -p $out
         nix build .#docs
 
         export out=/tmp/public/head-protocol/unstable
-
+mkdir -p $out
         cp result/build $out -r
 
         nix develop .#hydra-node-bench --command -- tx-cost --output-directory $out/benchmarks/