Tony Dow, who delighted audiences as big brother Wally Cleaver on the ’50s and ’60s sitcom “Leave It to Beaver,” died Tuesday at age 77. The actor announced in May that he was battling cancer, and in an update last week, Dow’s management team said he was experiencing complications from the disease. “Tony was a beautiful soul — kind, compassionate, funny and humble. It was truly a joy to just be around him,” his managers said Tuesday in an announcement of his death. “His gentle voice and unpretentious manner was immediately comforting and you could not help but love him.” The Los Angeles-born D…