unneeded include

Former-commit-id: d92285dad3710ccce531b9fef2172c6836a96ca8

tutorial/709_VectorFieldVisualizer/main.cpp

@@ -10,7 +10,6 @@
 #include <igl/slice.h>
 #include <igl/sort_vectors_ccw.h>
 #include <igl/streamlines.h>
-#include <igl/triangle_triangle_adjacency.h>
 #include <igl/copyleft/comiso/nrosy.h>
 #include <igl/viewer/Viewer.h>