build: upgrade AngularJS typings (#24583)

Previously, we were using [@types/angularjs][1], which is deprecated and
outdated (hasn't been updated for over two years). This PR switches to
[@types/angular][2], which is regularly updated (based on the
definitions on [DefinitelyTyped][3]).

[1]: https://www.npmjs.com/package/@types/angularjs
[2]: https://www.npmjs.com/package/@types/angular
[3]: https://github.com/DefinitelyTyped/DefinitelyTyped

PR Close #24583

packages/examples/tsconfig-build.json

@@ -11,7 +11,7 @@
       "rxjs/*": ["../../node_modules/rxjs/*"]
     },
     "outDir": "../../dist/examples",
-    "types": ["jasmine", "node", "angularjs", "systemjs"]
+    "types": ["jasmine", "node", "angular", "systemjs"]
   },
 
   "include": [