refactor(model-collection): updated toJSON typing

updated `toJSON` typing to track the model's `toJSON`

Author: nandi95

src/Calliope/ModelCollection.ts

@@ -418,7 +418,7 @@ export default class ModelCollection<T extends Model> extends Collection<T> {
     /**
      * @inheritDoc
      */
-    public override toJSON(): { elements: ReturnType<typeof JSON.parse>[] } {
+    public override toJSON(): { elements: Model['toJSON'][] } {
         // eslint-disable-next-line max-len
         // https://security.stackexchange.com/questions/7001/how-should-web-app-developers-defend-against-json-hijacking/7003#7003
         return { elements: this.toArray().map(model => model.toJSON()) };