By William Schomberg LONDON (Reuters) -British finance minister Rishi Sunak, a contender to become prime minister if Boris Johnson leaves office, set out his commitment to low taxes but said he would not slavishly cut the role of the state in the world’s fifth-biggest economy. Sunak set out his plan to help companies to invest more in capital and in research and development via tax incentives, even as the government’s tax take is set to reach its highest since the 1950s after he oversaw a huge increase in pandemic spending. “I firmly believe in lower taxes,” Sunak said in a speech on Thursday …