linkcheck: pass explicit -f - to tar when extracting from the curl pipe

Make stdin extraction explicit (tar -xzf -) rather than relying on GNU
tar's compiled-in default archive device. Backports the fix from
QuantEcon/lecture-python.myst#953 for consistency across the migrated
linkcheck workflows.

Co-Authored-By: Claude Opus 4.8 (1M context) <noreply@anthropic.com>

Author: mmcky

.github/workflows/linkcheck.yml

@@ -30,7 +30,7 @@ jobs:
         run: |
           set -euo pipefail
           mkdir -p _site
-          curl -fsSL "${{ steps.release.outputs.asset-url }}" | tar -xz -C _site
+          curl -fsSL "${{ steps.release.outputs.asset-url }}" | tar -xzf - -C _site
       - name: AI-Powered Link Checker
         uses: QuantEcon/action-link-checker@main
         with: