fix: use actions/cache@v5 for seed repo cache

Match the version used by the existing Playwright browser cache step.

Co-Authored-By: Claude Opus 4.6 <noreply@anthropic.com>

Author: gkorland

.github/workflows/playwright.yml

@@ -51,7 +51,7 @@ jobs:
         echo "flask=$(git ls-remote https://github.com/pallets/flask HEAD | cut -f1)" >> "$GITHUB_OUTPUT"
 
     - name: Cache seeded repository clones
-      uses: actions/cache@v4
+      uses: actions/cache@v5
       with:
         path: ${{ github.workspace }}/repositories
         key: ${{ runner.os }}-seed-repos-${{ hashFiles('e2e/seed_test_data.py') }}-${{ steps.seed-repo-shas.outputs.graphrag_sdk }}-${{ steps.seed-repo-shas.outputs.flask }}