mkosi: update fedora commit reference

mkosi: update fedora commit reference

* 28076e6232 Only make python3-pillow Recommends on Fedora
* a9807c4486 Do not require grubby on CentOS Stream 9
* d38cacfd3a Version 256.5
* 38291e13c1 Disable integration of userdb in sshd
* 53118d2112 Backport patch to only read /proc/cmdline when not in container
* 903e8e0f88 Backport upstream patch to try more initrd variants in 90-loaderentry.install
* b29a66006c Version 256.4
* 1cdae03391 Update tmpfiles --destroy-data patch
* 4fd4ef72a6 Upload sources
* 3c3772150d Version 256.3