“Practical Magic 2” conjures a box-office victory this weekend, topping the North American charts nearly three decades after its predecessor. The Warner Bros. sequel, starring Sandra Bullock and Nicole Kidman, earns an estimated $30 million from 4,146 theaters. The film knocks “Spider-Man: Brand New Day” out of the top spot after six consecutive weekends. The sequel reunites Bullock and Kidman as sisters Sally and Gillian Owens, members of a family of witches. The film introduces a younger generation of the Owens family, played by Joey King and Maisie Williams, and is adapted from the work of author Alice Hoffman.