Remove Duplicate Include

Also solves a problem with AnimatedSprites, when you add sprites for the animation the engine crash

scene/2d/animated_sprite.cpp

@@ -30,7 +30,6 @@
 #include "animated_sprite.h"
 #include "os/os.h"
 #include "scene/scene_string_names.h"
-#include "scene/scene_string_names.h"
 
 #define NORMAL_SUFFIX "_normal"