fix kestrel null reference exception (#340)

Found by dotnet/aspnetcore#28112 (comment)

Author: corneliusmunz

clients/ConsoleClientWithBrowser/ConsoleClientWithBrowser.csproj

@@ -11,7 +11,7 @@
   </ItemGroup>
 
   <ItemGroup>
-    <PackageReference Include="Microsoft.AspNetCore.Server.Kestrel" Version="2.2.0" />
+    <FrameworkReference Include="Microsoft.AspNetCore.App" />
     <PackageReference Include="Serilog.Extensions.Logging" Version="3.0.1" />
     <PackageReference Include="Serilog.Sinks.Console" Version="3.1.1" />
   </ItemGroup>