“Shang Chi” star Meng’er Zhang and “Upload” actor Robbie Amell have boarded the cast of “The Witcher” for the show’s upcoming third season. Henry Cavill will be back as Geralt of Rivia for season three of the fantasy show along with Freya Allan and Anya Chalotra, who play Ciri and Yennefer of Vengerberg, respectively. The third season will also feature …