Remove clause for newer compilers, fixes issue #64
Remove clause for newer compilers, fixes issue #64

Newer compilers (GCC 9.2) require loop's upper-bound variable to
be explicitly designated as private/shared/firstprivate/lastprivate
but that causes issue with older compilers (GCC 4.8.5 to 8.3.0).
Removing default(none) fixes it for old and new compilers.

hpcg-benchmark/hpcg,hpcg-benchmark/hpcg,hpcg-benchmark/hpcg,hpcg-benchmark/hpcg,hpcg-benchmark/hpcg,hpcg-benchmark/hpcg