Remove Session from Instant Messaging

[redoomed1]

update!: Require PFS for instant messengers and remove Session

For context, see

List Element under Social Networks + IM/RTC Page Changes

In addition to recommending Mastodon (Social Networking Software) I wish to move Element from the Real-Time Communications page to a new Social Networks page. I would consider public Discord servers to be far more akin to social networks than instant messaging, and I think we largely recommend Element to replace Discord for this specific use-case. After making this change, we would also: Fully require PFS for instant messengers. Previously we downranked instant messengers without PFS, to acc…