[Mod] requirements.txt: use cdn for wheels
[Mod] requirements.txt: use cdn for wheels

andrewchenshx/vnpy,bigdig/vnpy,bigdig/vnpy,msincenselee/vnpy,bigdig/vnpy,msincenselee/vnpy,andrewchenshx/vnpy,andrewchenshx/vnpy,msincenselee/vnpy,andrewchenshx/vnpy,msincenselee/vnpy,andrewchenshx/vnpy,vnpy/vnpy,bigdig/vnpy,vnpy/vnpy