Update web content to remove "Working Group"

There are a number of content updates that need to be made now that openMobility is not a working group.

https://docs.google.com/document/d/1Jj8M2KdYKZjbtKm-ojIAQb0vPfee1UfTyX7id3AQJmc/edit?usp=sharing

CC @scorbett