chore(deps): update pnpm to v9.15.9 (#2041)

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

Author: renovate[bot]

package.json

@@ -3,7 +3,7 @@
   "type": "module",
   "repository": "graphql/graphql.github.io website",
   "private": true,
-  "packageManager": "pnpm@9.15.2",
+  "packageManager": "pnpm@9.15.9",
   "scripts": {
     "build": "next build && next-image-export-optimizer",
     "check:links": "lychee --verbose --no-progress './src/pages/**/*.mdx' --base https://graphql.org",