Revert "[Add] metaclass of singleton"
Revert "[Add] metaclass of singleton"

This reverts commit b05eb7142e60fd3cb93e6b04e1c7e89746670462.

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