upgraded test sdk

Author: kerryjiang

test/SuperSocket.Tests/SuperSocket.Tests.csproj

@@ -19,7 +19,7 @@
     <PackageReference Include="Microsoft.Extensions.Options.ConfigurationExtensions" Version="$(MSExtensionsVersion)" />
     <PackageReference Include="Microsoft.Extensions.Hosting" Version="$(MSExtensionsVersion)" />
     <PackageReference Include="Microsoft.Extensions.Logging.Debug" Version="$(MSExtensionsVersion)" />
-    <PackageReference Include="Microsoft.NET.Test.Sdk" Version="16.0.1" />
+    <PackageReference Include="Microsoft.NET.Test.Sdk" Version="17.9.0" />
     <PackageReference Include="xunit" Version="2.4.0" />    
     <PackageReference Include="xunit.runner.visualstudio" Version="2.4.0" />
   </ItemGroup>