fix(docs): documentation fix for creater text in polymorphic relation

fix in docs for typo from "creater" to "creator"

Signed-off-by: Vaibhav Kumar <[email protected]>

docs/site/Polymorphic-relation.md

@@ -62,7 +62,7 @@ deliverable_type: string;
 
 The only difference on the repository class is that instead of having a single
 repository getter, a dictionary of subclass repository getters is passed into
-the repository factory creater.
+the repository factory creator.
 
 ```javascript
 export class DeliveryRepository extends DefaultCrudRepository {