Hi, I had the very same issue last night: running a bookworm system installed more than a year ago with buster's installer using the default encrypted scheme. The /boot partition cannot hold 2 initrd images and finish the installation of the new one because of a lack of disk space.
I had to temporarily move the old one out, let apt finish, reboot, move it back in and let apt remove it. I am aware that I could modify initramfs.conf's MODULES value to 'dep' to trim the image files. Nathan Lövsund Sent with [ProtonMail](https://protonmail.com/) Secure Email.
