/usr/lib/x86_64-linux-gnu/plplot5.13.0/drivers/xwin.driver_info is in plplot-driver-xwin 5.13.0+dfsg-6ubuntu2.
This file is owned by root:root, with mode 0o644.
The actual contents of the file can be viewed below.
1
xwin:X-Window (Xlib):1:xwin:5:xw