[winstackers][powervmstackers][tc] removing winstackers and PowerVMStackers from TC governance

Following the U cycle election there was no candidate for either the winstackers or powervmstackers team PTL role. This is the second cycle in a row where that problem has occurred for both teams, which indicates that the teams are not active in the community. During the TC meeting today [1] we discussed removing the teams from governance, so I have proposed the patches to do that [2][3].

Doug

[1] http://eavesdrop.openstack.org/meetings/tc/2019/tc.2019-09-05-14.00.log.html... [2] https://review.opendev.org/680438 remove powervmstackers team [3] https://review.opendev.org/680439 remove winstackers team