mkosi: update debian commit reference

mkosi: update debian commit reference

* 2d10c12bd5 Drop /etc/sysctl.d/99-sysctl.conf symlink
* fb73af0d22 update changelog
* 9d74923dd7 Move systemd-time-wait-sync to systemd-timesyncd package
* 8e0914aa0d Update changelog for 256.2-1 release
* 6dabf74a81 Install run0 zsh completion file
*   a72e454b2b Update upstream source from tag 'upstream/256.2'
|\
| * cf928e099f New upstream version 256.2
* c473d940f7 d/e/checkout-upstream: switch packaging branch on upstream stable PRs
* 13586fc76f d/e/checkout-upstream: do not fail if rebase fails
* 19785960d1 d/e/checkout-upstream: fix shellcheck warnings
* 72b215c3f0 Install zsh completion for run0
* 51f87a981e initramfs-tools: copy network drop-ins too