In English, the advancement "Sky's the Limit" means "there is no limit". However, the translate of Chinese is "天空即为极限", which means the sky is the limit.

In the game, players will get this advancement while they get an elytra, which allows players to fly in the sky freely. But "天空即为极限" means sky is a limit or a barrier, you cannot touch it. "Sky's the Limit" is an idiom that shoudn't be translated literally, its currect meaning is "没有限制", but the meaning of "即为" is "有，是". The true translation should be "天空并非极限".

Obviously, it's a translation error.

Changing it to "天空并非极限" can solve this problem.

In zh_cn.json from 1.20.4, line 113:
"advancements.end.elytra.title": "天空即为极限",