tests bsim ccc_store: Fix main return

Since 3a197934fc
main() should be int main(void) instead of void main(void)

Signed-off-by: Alberto Escolar Piedras <alberto.escolar.piedras@nordicsemi.no>

tests/bsim/bluetooth/host/gatt/ccc_store/src/main.c

@@ -81,7 +81,8 @@ struct bst_test_list *test_ccc_store_install(struct bst_test_list *tests)
 
 bst_test_install_t test_installers[] = {test_ccc_store_install, NULL};
 
-void main(void)
+int main(void)
 {
 	bst_main();
+	return 0;
 }