fix(router): update the version placeholder so that it gets replaced during the build

Fixes #17403

Author: IgorMinar

packages/router/src/version.ts

@@ -16,4 +16,4 @@ import {Version} from '@angular/core';
 /**
  * @stable
  */
-export const VERSION = new Version('0.0.0-ROUTERPLACEHOLDER');
+export const VERSION = new Version('0.0.0-PLACEHOLDER');