[3.0] Contribs: update libxml2 to 2.9.14
Fixes notably: CVE-2018-9251 CVE-2018-14567 CVE-2018-14404 CVE-2021-3541 CVE-2022-23308 CVE-2022-29824
And move to the official Gnome Infrastructure
(cherry picked from commit 471fd489) Signed-off-by: Jean-Baptiste Kempf jb@videolan.org