libraries/winpthreads: remove unused dwFlags variable in sched.c

the usage of this variable was removed in 13c9e28c0e77fb9877e0580139e769b1de55f6c7 commit

Signed-off-by: Biswapriyo Nath <nathbappai@gmail.com>
Signed-off-by: Liu Hao <lh_mouse@126.com>
1 file changed