Adele Springsteen, who nurtured the budding musical talent of her son, the pioneering rock star Bruce Springsteen, died on Wednesday. She was 98. Mr. Springsteen announced his mother’s death in an Instagram post on Thursday. It did not say where she died, and no cause was given. Ms. Springsteen had struggled with Alzheimer’s disease for more than a decade. Her son has been outspoken about his relationship with his mother and her influence on him. Ms. Springsteen rented him his first guitar when he was 7, he said in his Broadway show, “Springsteen on Broadway,” which had a long run in 2017, 2018…