Bug#945292: lightdm: needlessly(?) build-depends on deprecated gnome-doc-utils

[Andreas Henriksson <andreas@fatal.se>]

Source: lightdm
Version: 1.26.0-6
Severity: normal

Dear Maintainer,

I'm tired. Your package already build-depends on yelp-tools so I'm
going to just assume that the gnome-doc-utils build-dependency is
a leftover from before switching to yelp/itstool. I don't have the
energy left to build-test this for you. This message brought to you
because gnome-doc-utils has been deprecated for > 5 years and might
not survive to bullseye release because of the python2 removal.

Please drop the gnome-doc-utils build-dependency if it's not needed
(and if it is, please find another option soon).

Regards,
Andreas Henriksson