Top seed Ons Jabeur won the Berlin grass court WTA tournament on Sunday when her opponent, Olympic champion Belinda Bencic, retired with injury early in the second set. Eighth seed Bencic suffered the left leg injury in the last game of the first set. She continued heavily taped after an injury time-out but called it quits after the third game of the second set in which she served three double faults. Jabeur, 27, was leading 6-3, 2-1 at the time in stifling heat on the Steffi Graf Court. It was the third career title and second of the year for Tunisia’s Jabeur who will reach a career-high numb…