Add Kestrel.Core to PatchConfig.props

Author: halter73

eng/PatchConfig.props

@@ -20,6 +20,7 @@ Later on, this will be checked using this condition:
       Microsoft.AspNetCore.Server.IIS;
       Microsoft.AspNetCore.Server.IISIntegration;
       Microsoft.AspNetCore.Server.IntegrationTesting.IIS;
+      Microsoft.AspNetCore.Server.Kestrel.Core;
       Microsoft.AspNetCore.Server.Kestrel.Transport.Sockets;
       Microsoft.AspNetCore.Diagnostics.EntityFrameworkCore;
     </PackagesInPatch>