Fix compressed palette alignment

src/battle_arena.c

@@ -8,6 +8,7 @@
 #include "decompress.h"
 #include "event_data.h"
 #include "frontier_util.h"
+#include "graphics.h"
 #include "gpu_regs.h"
 #include "item.h"
 #include "m4a.h"
@@ -23,9 +24,6 @@
 #include "constants/battle_frontier.h"
 #include "constants/moves.h"
 
-extern const u32 gUnknown_08D854E8[];
-extern const u16 gUnknown_08D855E8[];
-
 // This file's functions.
 static void sub_81A58B4(void);
 static void sub_81A5964(void);