chore(deps): update pnpm to v8.15.6

Author: renovate[bot]

package.json

@@ -2,7 +2,7 @@
   "name": "@tresjs/post-processing",
   "type": "module",
   "version": "0.7.1",
-  "packageManager": "pnpm@8.11.0",
+  "packageManager": "pnpm@8.15.6",
   "description": "Post-processing library for TresJS",
   "author": "Alvaro Saburido <hola@alvarosaburido.dev> (https://github.com/alvarosabu/)",
   "license": "MIT",