Clean up wgs.yaml file

[anishasthana]

https://github.com/kubeflow/community/blob/master/wgs.yaml appears to contain a lot of inactive SIGS and WGs. Additionally, some of the active working groups appear to have inactive/inaccurate chairs and leads. We should run through the yaml and clean it up.

cc @kubeflow/kubeflow-steering-committee

[terrytangyuan]

some of the active working groups appear to have inactive/inaccurate chairs and leads

WG leads should help clean these up.