Remove kestrel reference

Author: Tratcher

src/Middleware/WebSockets/src/Microsoft.AspNetCore.WebSockets.csproj

@@ -13,7 +13,6 @@
 
   <ItemGroup>
     <Reference Include="Microsoft.AspNetCore.Http.Extensions" />
-    <Reference Include="Microsoft.AspNetCore.Server.Kestrel.Core" />
     <Reference Include="Microsoft.Extensions.Logging.Abstractions" />
     <Reference Include="Microsoft.Extensions.Options" />
   </ItemGroup>