Fixes after feedback Nc.

Actually, some months ago it was a bit slow. I'm on the cloud.netcloud.com with Nextcloud community. And it would take ages to load a chat with 200 unread.

But I just tested today, and it is fine. Maybe a bit slower than matrix, but not 2 times.

So I propose to simply remove this sentence.

I also updated the matrix: https://pad.liiib.re/fVeJwzTxTkKNPScJzFT4xA?view= (The changelog is at the bottom)