gnome-base/dconf: bump to 0.32.0, drop env.d snippet and vala deps

gnome-base/dconf: bump to 0.32.0, drop env.d snippet and vala deps

Long ago we added a /etc/env.d/51dconf for forcing GSETTINGS_BACKEND=dconf
into the environment when dconf is installed - presumably to switch over to
it from gconf. However nowadays dconf already has the highest priority out
of the available gsettings backend extension points, thus this has become
long unnecessary, and if GSETTINGS_BACKEND is unset and dconf is installed,
it'll pick dconf still too.

dconf-0.32 ported its dconf command line utility away from vala to straight
C, and thus vala is not necessary anymore. It is necessary (the vapigen.pc
file in particular) upstream for finding the location where to install the
pregenerated dconf.vapi and dconf.deps files, but I've patched it to just
fallback to the well-established location of ${datadir}/vala/vapi/ and thus
can keep shipping vapi file without introducing a USE flag and vala deps.

Closes: https://bugs.gentoo.org/693472
Package-Manager: Portage-2.3.69, Repoman-2.3.12
Signed-off-by: Mart Raudsepp <leio@gentoo.org>