Developers who have apps in the Dice subcategory have received the email. Apple says that developers don't need to take any action, but can change their app's subcategory if desired.
Starting today, the Dice subcategory under Games will no longer be available for selection in iTunes Connect and will be removed from the App Store in the future. You are receiving this email because you have one or more apps in this subcategory.Apple did not explain why it has opted to remove the Dice category from the App Store, but it's likely not a highly popular category and its elimination allows for better streamlining of the available sections in the App Store.
While no action is required since subcategory selection is optional, you can change your app's subcategory during your next update as described in View and edit app information, or change it now if your app has an editable app status.
Lotto Machine has maintained #12 in the Dice category for quite a while ☹️ I guess now I'm a nothing in the games category instead pic.twitter.com/5WkfsWwaUV— Steve T-S (@stroughtonsmith) October 4, 2017
Dice games can be rolled into a wide range of other categories. Game categories in the revamped App Store in iOS 11 include Action, Adventure, AR, Arcade, Board, Card, Casino, Family, Indie, Kids, Music, Puzzle, Racing, Role Playing, Simulation, Sports, Strategy, Trivia, and Word.
Update: Apple is also removing the Educational Games subcategory and the Catalogs category from the Apps section of the App Store.