Replace `FindSkuById` with `GetSkuById`

plugins/FlashSales/src/EasyAbp.EShop.Plugins.FlashSales.Application/EasyAbp/EShop/Plugins/FlashSales/FlashSalesPlans/FlashSalesPlanAppService.cs

@@ -88,18 +88,13 @@ public class FlashSalesPlanAppService :
         await CheckMultiStorePolicyAsync(input.StoreId, CreatePolicyName);
 
         var product = await ProductAppService.GetAsync(input.ProductId);
-        var productSku = product.FindSkuById(input.ProductSkuId);
+        product.GetSkuById(input.ProductSkuId);
 
         if (product.StoreId != input.StoreId)
         {
             throw new ProductIsNotInThisStoreException(input.ProductId, input.StoreId);
         }
 
-        if (productSku == null)
-        {
-            throw new ProductSkuIsNotFoundException(input.ProductSkuId);
-        }
-
         var flashSalesPlan = new FlashSalesPlan(
             GuidGenerator.Create(),
             CurrentTenant.Id,
@@ -121,18 +116,13 @@ public class FlashSalesPlanAppService :
         await CheckMultiStorePolicyAsync(input.StoreId, UpdatePolicyName);
 
         var product = await ProductAppService.GetAsync(input.ProductId);
-        var productSku = product.FindSkuById(input.ProductSkuId);
+        product.GetSkuById(input.ProductSkuId);
 
         if (product.StoreId != input.StoreId)
         {
             throw new ProductIsNotInThisStoreException(input.ProductId, input.StoreId);
         }
 
-        if (productSku == null)
-        {
-            throw new ProductSkuIsNotFoundException(input.ProductSkuId);
-        }
-
         var flashSalesPlan = await GetEntityByIdAsync(id);
 
         flashSalesPlan.SetTimeRange(input.BeginTime, input.EndTime);