SpAdd handle: delete sort_option getter/setter (#2296)

SpAdd handle was originally a copy-paste of the spgemm
handle way back in #122, and included get_sort_option() and
set_sort_option() from spgemm. But these try to use the member
bool sort_option, which doesn't exist. Somehow these functions never
produced compile errors until someone tried to call them.

sparse/src/KokkosSparse_spadd_handle.hpp

@@ -102,10 +102,6 @@ class SPADDHandle {
    */
   size_type get_c_nnz() { return this->result_nnz_size; }
 
-  void set_sort_option(int option) { this->sort_option = option; }
-
-  int get_sort_option() { return this->sort_option; }
-
 #ifdef KOKKOSKERNELS_ENABLE_TPL_CUSPARSE
   SpaddCusparseData cusparseData;
 #endif