Actress Estelle Harris, who played Estelle Costanza on the hit sitcom “Seinfeld,” has died. The 93-year-old Manhattan native is said to have died Saturday. Monday would have been her 94th birthday. Jason Alexander, who played her son, George Costanza, on the hit NBC sitcom tweeted his condolences. “One of my favorite people has passed — my tv mama, Estelle Harris,” he wrote Sunday. “The joy of playing with her and relishing her glorious laughter was a treat. I adore you, Estelle. Love to your family. Serenity now and always.” That was a reference to a 1997 “Seinfeld” episode in which Jerry Sti…