Bug#1051728: libgusb: Out of date debian/watch and new upstream release

[Jeremy Bícha]

Source: libgusb
Version: 0.4.5-1.1

The latest releases of libgusb are being published at
https://github.com/hughsie/libgusb/releases instead of at the
people.freedesktop.org site.

The latest release is 0.4.6

Thank you,
Jeremy Bícha