Update AABB.cpp

Deleted duplicate include lines

Former-commit-id: c7e0a698a5e5ac406e737f7e0db55e0389a2f9fd

include/igl/AABB.cpp

@@ -10,7 +10,6 @@
 #include "barycenter.h"
 #include "barycentric_coordinates.h"
 #include "colon.h"
-#include "colon.h"
 #include "doublearea.h"
 #include "matlab_format.h"
 #include "point_simplex_squared_distance.h"