Revert "Use unified core mode for Silverblue & Kinoite"
Reverted while we investigate an installation failure.
See: https://pagure.io/pungi-fedora/pull-request/1115
This reverts commit c6e3cb1b5b011a7a1c5da6dba0195674acc41c70.
Signed-off-by: Timothée Ravier <tim@siosm.fr>