Libretro: Remove GBA LCD filter

Libretro use shaders for filters etc.

src/libretro/UtilRetro.cpp

@@ -238,12 +238,16 @@ void utilUpdateSystemColorMaps(bool lcd)
         for (int i = 0; i < 0x10000; i++) {
             systemColorMap16[i] = ((i & 0x1f) << systemRedShift) | (((i & 0x3e0) >> 5) << systemGreenShift) | (((i & 0x7c00) >> 10) << systemBlueShift);
         }
+        if (lcd)
+            gbafilter_pal(systemColorMap16, 0x10000);
     } break;
     case 24:
     case 32: {
         for (int i = 0; i < 0x10000; i++) {
             systemColorMap32[i] = ((i & 0x1f) << systemRedShift) | (((i & 0x3e0) >> 5) << systemGreenShift) | (((i & 0x7c00) >> 10) << systemBlueShift);
         }
+        if (lcd)
+            gbafilter_pal32(systemColorMap32, 0x10000);
     } break;
     }
 }