In the documentation above it says that you can go to: http://<Server Name>/<Site Name>/_vti_bin/ReportServer/ReportExecution2006.asmx?wsdl when using SharePoint Integrated mode.
There is no such thing as ReportExecution2006 web service. In SharePoint integrated mode you still use the ReportExecution2005 web service. The only difference between SharePoint Integrated mode and native mode is the management web service (ReportService2006 and ReportService2005).