fix(Cascader): hide arrow icon when hover (#6926)

Author: ArgoZhang

src/BootstrapBlazor/Components/Cascader/Cascader.razor.cs

@@ -203,7 +203,7 @@ private void SetDefaultValue(string defaultValue)
 
     private string? ClassString => CssBuilder.Default("select cascade menu dropdown")
         .AddClass("disabled", IsDisabled)
-        .AddClass("cls", IsClearable)
+        .AddClass("is-clearable", IsClearable)
         .AddClass(CssClass).AddClass(ValidCss)
         .Build();