message: Replace sheetClass example in CONTRIBUTING.md
  Those values will disappear in the config in v9. This now uses the
  collection property instead.
diff: @@ -153,21 +153,21 @@ If the type is not configurable by the user, it should most likely be `Construct
  allow deriving classes to be used as value. In rare occasions (i.e. when really only instances of this specific class
  may be assigned, no deriving classes), `typeof NameOfTheClass` can be used.
  -Example (`documentClass` is configurable, `sheetClass` is not):
  +Example (`documentClass` is configurable, `collection` is not):
  ```typescript
  /**
  - * Configuration for the ActiveEffect embedded document type
  + * Configuration for the Actor document
  */
  - ActiveEffect: {
  + Actor: {
  /**
  - * @defaultValue `ActiveEffect`
  + * @defaultValue `Actor`
  */
  - documentClass: ConfiguredDocumentClassOrDefault<typeof ActiveEffect>;
  + documentClass: ConfiguredDocumentClassOrDefault<typeof Actor>;
  /**
  - * @defaultValue `ActiveEffectConfig`
  + * @defaultValue `Actors`
  */
  - sheetClass: ConstructorOf<ActiveEffectConfig>;
  + collection: ConstructorOf<Actors>;
  };
  ```
  