By Pavel Polityuk KYIV (Reuters) -Ukraine said 50 civilians were evacuated from a bombed-out steelworks in the city of Mariupol on Friday, accusing Russia of violating a truce intended to allow dozens more still trapped beneath the plant to depart after weeks under siege. Mariupol has endured the most destructive bombardment of the 10-week-old war, and the sprawling Soviet-era Azovstal plant is the last part of the city – a strategic southern port on the Azov Sea – still in the hands of Ukrainian fighters. Ukrainian presidential adviser Oleksiy Arestovych said Russia was trying to finish off f…