Update release team staffing information
Update release team staffing information

Latest updates from [Dawn](https://groups.google.com/d/msg/kubernetes-dev/M-YDooHvE3s/JagsfnnTBQAJ)
  - Branch Manager: Chao Xu
  - Upgrade Testing: Jeff Regan
  - Patch Release Manager: Wojciech Tyczynski
kubernetes/enhancements,kubernetes/enhancements,kubernetes/enhancements