Remove LZMA support

[marcospb19]

As pointed out by @bczhc at #522:

Actually xz has some difference with LZMA format (xz --format=xz vs xz --format=lzma). IMO xz is a container format of LZMA2 format, which is a successor of the lagacy LZMA format.

We're using .lzma interchangeably with .xz, but that's incorrect.