NixOS 25.05 which distributed lowdown < 1.4 has been EOL for a bit now,
25.11 ships lowdown 2.0.4.
Dropping support means we can tweak the lowdown options for terminal
output which have been added in 1.4.0 without having diverging behavior
in possible builds of Lix.
Change-Id: Icae97cf5e9e680766b8a6f4e85514f4c4625d1dd
