Update src/cart_cell.cc

Co-authored-by: github-actions[bot] <41898282+github-actions[bot]@users.noreply.github.com>

Author: salva24

src/cart_cell.cc

@@ -22,6 +22,7 @@
 #include "cart_cell.h"
 #include <cstdint>
 #include "core/container/math_array.h"
+#include "core/functor.h"
 #include "core/interaction_force.h"
 #include "core/real_t.h"
 #include "core/resource_manager.h"