message: Fix deprecation for System class
diff: import type { Renderer } from './Renderer';
  +import { deprecation } from '@pixi/utils';
  /**
  * Interface for systems used by the {@link PIXI.Renderer}.
  + * @memberof PIXI
  */
  export interface ISystem
  {
  @@ -20,3 +22,32 @@ export interface ISystemConstructor<R = Renderer>
  {
  new (renderer: R): ISystem;
  }
  +
  +/**
  + * Use the ISystem interface instead.
  + * @deprecated since 6.1.0
  + * @memberof PIXI
  + */
  +export class System implements ISystem
  +{
  + /** Reference to the main renderer */
  + public renderer: Renderer;
  +
  + /**
  + * @param renderer - Reference to Renderer
  + */
  + constructor(renderer: Renderer)
  + {
  + // #if _DEBUG
  + deprecation('6.1.0', 'System class is deprecated, implemement ISystem interface instead.');
  + // #endif
  +
  + this.renderer = renderer;
  + }
  +
  + /** Destroy and don't use after this. */
  + destroy(): void
  + {
  + this.renderer = null;
  + }
  +}
  