Don't set initramfs compression to zstd as it's the default now[1]

[1] https://archlinux.org/news/moving-to-zstandard-images-by-default-on-mkinitcpio/
6 jobs for mkinitcpio-zstd in 22 minutes and 10 seconds (queued for 2 seconds)
Status Name Job ID Coverage
  Lint
passed shellcheck #15891

00:00:14

passed shfmt #15892

00:00:10

 
  Build
passed build #15893
fast-single-thread

00:18:14

 
  Test
passed test-basic-qemu #15895
fast-single-thread

00:02:58

passed test-cloudimg-qemu #15896
fast-single-thread

00:03:38

passed test-vagrant-boxes-format #15894

00:00:37