With the latest dev build (3189), I am getting this kind of autocomplete :
but previously I used to get this kind of autocomplete
How do I disable the first in order to get the second ? Please also note that I am using LSP
Note : When I press the backspace button , the original popup (from the second screenshot) appears
Not sure about the first popup, but the 2nd and 3rd are from LSP, I think. Maybe an update of the language server causing this new style of messages? ST does not provide such popups out of the box.
To be honest, my first thought was that the sublime devs started to implement the LSP protocol 
Cause that pop-up is nothing like that pop-up that comes with LSP(the plugin)
But as deathaxe said, maybe the language server returned something strange.
Is it happening for you guys as well or just me ? Perhaps I can reinstall everything and see if that fixes it ? BTW - I have also created a report on LSP’s Github repo.