<EnablePreviewFeatures> for HttpStress (#59410)

Author: antonfirsov

src/libraries/System.Net.Http/tests/StressTests/HttpStress/HttpStress.csproj

@@ -5,6 +5,7 @@
     <TargetFramework>net6.0</TargetFramework>
     <LangVersion>preview</LangVersion>
     <Nullable>enable</Nullable>
+    <EnablePreviewFeatures>True</EnablePreviewFeatures>
   </PropertyGroup>
 
   <ItemGroup>
@@ -21,4 +22,4 @@
     <PackageReference Include="Microsoft.AspNetCore.Server.Kestrel.Transport.Quic" Version="6.0.0-preview.5.21301.17" />
   </ItemGroup>
 
-</Project>
+</Project>