SINGAPORE: Robert Kubica announced on Thursday he will leave former champions Williams at the end of the year, a move likely to bring down the curtain on his extraordinary Formula One racing comeback.The 34-year-old made his return in 2019, eight years after suffering near-fatal injuries including a partially severed right arm in a minor rally in Italy on the eve of the 2011 season.”I have taken the decision that I will not continue more with Williams after this year,” he said at the Singapore Grand Prix.