Update pnpm/action-setup action to v6 (#167)

Co-authored-by: renovate[bot] <29139614+renovate[bot]@users.noreply.github.com>

Author: renovate[bot]

.github/workflows/pr-frontend.yaml

@@ -20,7 +20,7 @@ jobs:
       - uses: actions/checkout@v6
 
       - name: Set up pnpm
-        uses: pnpm/action-setup@v5
+        uses: pnpm/action-setup@v6
         with:
           package_json_file: frontend/package.json