Update event flag index for frlg

was block2+0x64
8*((0xF80-0xEE0)+0x64) = 0x820

this highlights a critical flaw in event flag reading; it expects the
region to be contiguous in the savedata. it's not. that's super bad, and
event flag r/w for flags >1280 won't work until I work something out

PKHeX.Core/Saves/SAV3.cs

@@ -410,7 +410,7 @@ namespace PKHeX.Core
                 if (Version == GameVersion.FRLG)
                     return 800; // dec
                 if (Version == GameVersion.RS)
-                    return 0x807; // hex
+                    return 0x820; // hex
                 return 0x867; // emerald
             }
         }