/usr/share/gdm/greeter/autostart/spice-vdagent.desktop is in spice-vdagent 0.17.0-1ubuntu2.
This file is owned by root:root, with mode 0o777.
It is a symlink to /etc/xdg/autostart/spice-vdagent.desktop
/etc/xdg/autostart/spice-vdagent.desktop