By Jonathan Landay, Tom Balmforth and Max Hunder BLAHODATNE, Ukraine/KYIV (Reuters) -Russia announced the completion of its withdrawal from the strategic city of Kherson in southern Ukraine on Friday and a regional official said Ukrainian partisans had raised a flag there, but that many Russian troops had been unable to leave. Reuters could not immediately verify the full extent of Ukraine’s advance, the status of Russia’s retreat or the fate of any Russian soldiers who may have been left behind as Moscow rushed to pull its troops across the wide Dnipro River. Serhiy Khlan, a member of Ukraine…