fix(ci): declare variable with export modifier to treat it as a env var

.github/workflows/validate-renovate.yml

@@ -25,7 +25,7 @@ jobs:
           package="renovate@=$ver"
           echo "npx: $(npx --version)"
           echo "installing: $package..."
-          H="$(mktemp)"
+          export H="$(mktemp)"
           
           # let's do main part, but avoid pipefail
           (npx --yes --package "$package" -- renovate-config-validator --strict || true)\