remove usum early return for dex bit setting

I highly doubt this is causing save corruption; looked through the
disassembly and the offset ptrs are the same relative to sun/moon.
Implementation is flexible for both as gamefreak allocated enough space
in each bit array.

pokedex editor recognizes bools correctly (including for formes).

PKHeX.Core/Saves/SAV7.cs

@@ -974,9 +974,6 @@ protected override void SetDex(PKM pkm)
             if (pkm.IsEgg) // do not add
                 return;
 
-            if (USUM) // TODO: IMPLEMENT POKEDEX EDITING FOR USUM
-                return;
-
             int bit = pkm.Species - 1;
             int bd = bit >> 3; // div8
             int bm = bit & 7; // mod8