fix(docs): Remove unused import "WishlistItem" from resolver snippet (#3334)

docs/docs/guides/developer-guide/plugins/index.mdx

@@ -519,7 +519,6 @@ Now that we have defined the GraphQL schema extensions, we need to create a reso
 import { Args, Mutation, Query, Resolver } from '@nestjs/graphql';
 import { Allow, Ctx, Permission, RequestContext, Transaction } from '@vendure/core';
 
-import { WishlistItem } from '../entities/wishlist-item.entity';
 import { WishlistService } from '../services/wishlist.service';
 
 @Resolver()