No, HBO didn't change the title. Even title Death is the Enemy is not the official title, Beyond the Walls is.
From this source (might contain spoilers)
This week’s official Game of Thrones preview. As of publication, HBO still hadn’t released an official name for the episode. UPDATE! The official title is “Beyond the Wall.”
From the same page,
We open north of the Wall. Ser Beric says in voice over: “Death is the enemy.”
This is what might have made fans think that the title is Death is the Enemy.
Other sources such as UPROXX also says the same.
Here is the official tweet.
“Beyond the Wall” premieres at 9PM on @HBO. #GoTS7 pic.twitter.com/wMYagT02Pb
— Game Of Thrones (@GameOfThrones) August 20, 2017