Update description of Participation in Section 7

[SpencerDawkins]

Both IETF and 3GPP have figured out how to work with remote participants in ways that weren't possible in 2002. The constraints are now administrative, not technical.

If the IETF can commit to hybrid onsite/remote meetings for the foreseeable future, and we can say that in the document, that would be helpful.

I'm not quite sure where 3GPP is on remote participation, but I'm sure someone on the coordination team could explain it, and then we can figure out what we can say in the document.