test(Localizer): remove net9 localizer test (#7132)

Author: ArgoZhang

test/UnitTest/Utils/UtilityTest.cs

@@ -10,7 +10,6 @@
 using System.ComponentModel.DataAnnotations;
 using System.Data;
 using System.Globalization;
-using System.Net;
 using System.Reflection;
 using UnitTest.Components;
 
@@ -393,12 +392,7 @@ public void GetJsonStringByTypeName_UseKeyWhenValueIsNull()
 
         var test1 = items.FirstOrDefault(i => i.Name == "Test-Null");
         Assert.NotNull(test1);
-
-#if NET9_0
-        Assert.Equal("", test1.Value);
-#elif NET10_0_OR_GREATER
         Assert.Equal("Test-Null", test1.Value);
-#endif
 
         var test2 = items.FirstOrDefault(i => i.Name == "Test-Key");
         Assert.NotNull(test2);