build: update pnpm to v9.15.9

See associated pull request for more information.

(cherry picked from commit adaa742)

Author: angular-robot

package.json

@@ -32,7 +32,7 @@
     "type": "git",
     "url": "https://github.com/angular/angular-cli.git"
   },
-  "packageManager": "[email protected].6",
+  "packageManager": "[email protected].9",
   "engines": {
     "node": "^20.11.1 || >=22.11.0",
     "npm": "Please use pnpm instead of NPM to install dependencies",