Clarify process to remove WG leads/approvers

[bsnchan]

Currently, WG leads/approvers can self remove themselves but it's unclear what the process is for the community to remove a WG lead/approver.

Let's:

• Document that we expect folks to self remove themselves as the default process
• Document what process community members should follow to remove a WG lead/approver

[bsnchan]

/assign @pmorie

I believe you said you would take this AI at our steering committee meeting?

[pmorie]

This is closed by #111