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

This addresses GHSA-fxqj-rqcc-2cmp

TAG=agy

CONV=63a146aa-f34e-4200-88d1-90537150adb0

Author: alan-agius4

packages/angular/build/package.json

@@ -55,7 +55,7 @@
     "jsdom": "28.1.0",
     "less": "4.4.2",
     "ng-packagr": "21.2.3",
-    "postcss": "8.5.12",
+    "postcss": "8.5.23",
     "rxjs": "7.8.2",
     "vitest": "4.0.18"
   },