doc: 更新文档示例

Author: ArgoZhang

src/BootstrapBlazor.Server/Components/Samples/Dropdowns.razor

@@ -37,7 +37,7 @@
             <Dropdown TValue="string" Items="Items" ShowSplit="true" Color="Color.Primary"></Dropdown>
         </div>
         <div class="col-6 col-sm-4 col-md-3">
-            <Dropdown TValue="string" Items="Items" ShowSplit="false" Color="Color.Info"></Dropdown>
+            <Dropdown TValue="string" Items="Items" ShowSplit="true" Color="Color.Info"></Dropdown>
         </div>
         <div class="col-6 col-sm-4 col-md-3">
             <Dropdown TValue="string" Items="Items" ShowSplit="true" Color="Color.Warning"></Dropdown>