build: update ng-packagr to stable version

Author: alan-agius4

packages/schematics/angular/utility/latest-versions/package.json

@@ -12,7 +12,7 @@
     "karma-jasmine-html-reporter": "~2.0.0",
     "karma-jasmine": "~5.1.0",
     "karma": "~6.4.0",
-    "ng-packagr": "^15.0.0-next.0",
+    "ng-packagr": "^15.0.2",
     "protractor": "~7.0.0",
     "rxjs": "~7.5.0",
     "tslib": "^2.3.0",