The mods name is "Instant Lava"
Here's the link to it: https://www.curseforge.com/minecraft/mc-mods/instantlava
Version ; Fabric 1.16.2
Mod content: make lava infinite like water
In Feb 8th 2020 A user has requested it and it seem that the aternos hasn't add it in fabric 1.16.2 so please add it