By Andrew MacAskill LONDON (Reuters) – British Prime Minister Rishi Sunak faces a parliamentary showdown with right-wing lawmakers in his party this week as his legislation to block legal challenges to the plan to deport asylum seekers to Rwanda returns to parliament. The British government is trying to reduce a surge in asylum seekers who make the dangerous crossing in small boats from France to the southern coast of England. Most of those arriving in the boats say they are fleeing wars and poverty in the Middle East, Africa and South Asia. But the British government says about 90% making the…