From the Microsoft blog post:
We have removed the Wi-Fi Sense feature that allows you to share Wi-Fi networks with your contacts and to be automatically connected to networks shared by your contacts. The cost of updating the code to keep this feature working combined with low usage and low demand made this not worth further investment. Wi-Fi Sense, if enabled, will continue to get you connected to open Wi-Fi hotspots that it knows about through crowdsourcing.
Also, from Jason on the Insider team, on Twitter:
FM Radio has been removed from dev branch builds and is being cut. May use third party radio apps from store.
FM radio is somewhat niche in 2016, in a phone, but is probably a much bigger deal in the developing world. Still, as Microsoft says, there are third party applications (e.g. this one) which liase with your phone's receiver to produce audio. Comments welcome if you have a favourite app along these lines...
It's good to see Microsoft actively pruning its OS and code in these ways. I do worry about what's next to be axed though, in the great big code clean-up for Redstone and beyond.
More as it happens, no doubt. We do expect a new Redstone Insiders build this week.