By Saikat Chatterjee LONDON (Reuters) -The British pound dropped to a two-year low on Monday as traders moved to the sidelines as a leadership contest kicked off to determine Britain’s next prime minister. Worsening risk appetite before the all-important U.S. inflation data this week sent the dollar surging against its main rivals. [FRX/] Boris Johnson’s resignation as prime minister deepened the uncertainty hanging over the British economy, already under strain from an inflation rate heading for double digits, the risk of a recession and Brexit. Whoever succeeds Johnson must take big decision…