CI: Use actions/setup-node pnpm cache for deploy; remove redundant pnpm store cache steps

Author: ndbroadbent

.github/workflows/deploy-site.yml

@@ -39,24 +39,15 @@ jobs:
         uses: actions/setup-node@v4
         with:
           node-version: '20'
+          cache: 'pnpm'
+          cache-dependency-path: 'site/pnpm-lock.yaml'
 
       - name: Setup pnpm
         uses: pnpm/action-setup@v4
         with:
           version: latest
 
-      - name: Get pnpm store directory
-        shell: bash
-        run: |
-          echo "STORE_PATH=$(pnpm store path --silent)" >> $GITHUB_ENV
-
-      - name: Setup pnpm cache
-        uses: actions/cache@v4
-        with:
-          path: ${{ env.STORE_PATH }}
-          key: ${{ runner.os }}-pnpm-store-${{ hashFiles('**/pnpm-lock.yaml') }}
-          restore-keys: |
-            ${{ runner.os }}-pnpm-store-
+      # Rely on actions/setup-node pnpm cache; no manual pnpm store cache needed
 
       - name: Install site dependencies
         run: |