fix(@angular/build): upgrade postcss to 8.5.23

This addresses GHSA-fxqj-rqcc-2cmp

Author: alan-agius4

packages/angular/build/package.json

@@ -54,7 +54,7 @@
     "jsdom": "26.1.0",
     "less": "4.4.0",
     "ng-packagr": "20.3.0",
-    "postcss": "8.5.12",
+    "postcss": "8.5.23",
     "rxjs": "7.8.2",
     "vitest": "3.2.4"
   },