readme: Stop recommending setuid bit for non-logind systems

- Optional since Sway 1.6 per swaywm/wlroots@bad1e9afa8
- Deprecated in Sway 1.7 per 67d3d952b6
- Removed in Sway 1.8 per e5728052b5
- Ignored in future versions (keeps root priveleges)

README.md

@@ -43,12 +43,6 @@ Run these commands:
     ninja -C build/
     sudo ninja -C build/ install
 
-On systems without logind nor seatd, you need to suid the sway binary:
-
-    sudo chmod a+s /usr/local/bin/sway
-
-Sway will drop root permissions shortly after startup.
-
 ## Configuration
 
 If you already use i3, then copy your i3 config to `~/.config/sway/config` and