Fix SSH key regeneration service hanging on boot

Remove ExecStartPost that was calling systemctl restart ssh, which
caused a deadlock. The Before=ssh.service ordering ensures keys are
generated before ssh starts - no restart needed.

🤖 Generated with [Claude Code](https://claude.com/claude-code)

Co-Authored-By: Claude Opus 4.5 <noreply@anthropic.com>

rpi/sanitize-for-image.sh

@@ -126,7 +126,6 @@ ConditionPathExists=!/etc/ssh/ssh_host_ed25519_key
 [Service]
 Type=oneshot
 ExecStart=/usr/bin/ssh-keygen -A
-ExecStartPost=/bin/systemctl restart ssh
 
 [Install]
 WantedBy=multi-user.target