[MC-184482] End Gateways don't generate after defeating the ender dragon

Moderator Note

This issue was resolved for all saves not opened in 20w20b or 20w21a - if you did open your world in those versions, you may need to manually edit your level.dat to get a gateway to spawn.

I just killed the Ender Dragon in survival world in new snapshot and the gateway didn't spawned, then i killed it in creative world and the gateway still doesn't spawn. I even killed dragon for second time and still doesn't spawn. I don't think I just didn't found the gateway because I made render distance 32 chunks and in the survival world I even cheated and entered the spectator mode and I still didn't found it. Also sorry for mistakes if I made some, I'm not very good in english.