chore(deps): update pnpm to v8.15.2 (#9024)

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

Author: renovate[bot]

package.json

@@ -7,7 +7,7 @@
   "license": "MIT",
   "repository": "https://github.com/keystonejs/keystone",
   "homepage": "https://github.com/keystonejs/keystone",
-  "packageManager": "pnpm@8.15.1",
+  "packageManager": "pnpm@8.15.2",
   "scripts": {
     "coverage": "jest --coverage",
     "test": "jest",