ci: pin pnpm setup version for template smoke

Author: choisungyong

.github/workflows/ci.yml

@@ -569,10 +569,9 @@ jobs:
         run: bash scripts/test-templates.sh
 
       - name: Install pnpm
-        # version is auto-detected from root package.json `packageManager` field
-        # (pnpm@9.15.0). Specifying `version:` here would conflict with that
-        # and fail with ERR_PNPM_BAD_PM_VERSION.
         uses: pnpm/action-setup@v6
+        with:
+          version: 9.15.0
 
       - uses: actions/setup-node@v4
         with: