added licence to the new test file

test/c/test_interpolation_vector.cpp

+// ICON
+//
+// ---------------------------------------------------------------
+// Copyright (C) 2004-2024, DWD, MPI-M, DKRZ, KIT, ETH, MeteoSwiss
+// Contact information: icon-model.org
+//
+// See AUTHORS.TXT for a list of authors
+// See LICENSES/ for license information
+// SPDX-License-Identifier: BSD-3-Clause
+// ---------------------------------------------------------------
+
 #include <gtest/gtest.h>
 #include <Kokkos_Core.hpp>
 #include <vector>