iso: fix packages.x86_64 (no inline comments; gstreamer-vaapi -> gst-plugin-va)

Inline comments after a package name broke kitty/flatpak (became invalid
names with trailing whitespace). gstreamer-vaapi was removed from Arch.
calamares is AUR-only -> commented pending a [tanin] rebuild decision.

Co-Authored-By: Claude Opus 4.8 <noreply@anthropic.com>

iso/build-profile/airootfs/etc/mkinitcpio.d/linux.preset

@@ -0,0 +1,8 @@
+# mkinitcpio preset file for the 'linux' package on archiso
+
+PRESETS=('archiso')
+
+ALL_kver='/boot/vmlinuz-linux'
+archiso_config='/etc/mkinitcpio.conf.d/archiso.conf'
+
+archiso_image="/boot/initramfs-linux.img"