Conductor Lorin Maazel won’t be able to lead the Boston Symphony Orchestra on its upcoming tour of Japan and China, the BSO announced Monday morning. Taking his place will be Swiss conductor Charles Dutoit. Maazel is dropping out on the advice of his doctors due to an accident, the BSO said in a release. The tour runs from May 1 to 10 and includes the BSO’s first dates in China since 1979. Earlier this month, Maazel, 84, dropped out of concerts at Carnegie Hall, where he was to have led the Munich Philharmonic Orchestra.