OpenMP backend no longer requires volatile for Kokkos::single in a TeamPolicy

[cwpearson]

kokkos/kokkos#5452 may cause this use of volatile to produce a compile-time error. This volatile qualifier can be removed.

kokkos-kernels/sparse/impl/KokkosSparse_bspgemm_impl_kkmem.hpp

Line 465 in ee0f695

volatile nnz_lno_t *tmp = NULL;

kokkos-kernels/sparse/impl/KokkosSparse_bspgemm_impl_kkmem.hpp

Lines 475 to 476 in ee0f695

	[&](volatile nnz_lno_t *&memptr) {
	memptr = (volatile nnz_lno_t *)(memory_space.allocate_chunk(

kokkos-kernels/sparse/impl/KokkosSparse_bspgemm_impl_kkmem.hpp

Line 617 in ee0f695

volatile nnz_lno_t *tmp = NULL;

kokkos-kernels/sparse/impl/KokkosSparse_bspgemm_impl_kkmem.hpp

Lines 624 to 625 in ee0f695

	[&](volatile nnz_lno_t *&memptr) {
	memptr = (volatile nnz_lno_t *)(memory_space.allocate_chunk(