Open first user after deleting one.

Current behavior opens the DefaultUserId, however with the change to use
a randomly generated ID for the first user there is not a user with that
ID. Instead we open the first user in _profiles.

src/Ryujinx.HLE/HOS/Services/Account/Acc/AccountManager.cs

@@ -187,7 +187,7 @@ namespace Ryujinx.HLE.HOS.Services.Account.Acc
 
             _profiles.Remove(userId.ToString(), out _);
 
-            OpenUser(DefaultUserId);
+            OpenUser(new UserId(_profiles.First().Key));
 
             _accountSaveDataManager.Save(_profiles);
         }