fix(cdk-platform): pass {} to @NgModule since passing nothing breaks (#13792)

in JIT mode

Author: mmalerba

src/cdk/platform/platform-module.ts

@@ -9,5 +9,5 @@
 import {NgModule} from '@angular/core';
 
 
-@NgModule()
+@NgModule({})
 export class PlatformModule {}