databases/libgda6: Unbreak build with libxml2 2.14

Unbreak the build after the libxml2 upgrade. The PORTREVISION was bumped
for the libxml2 upgrade to no need to do it again.

Upstream issue: https://gitlab.gnome.org/GNOME/libgda/-/issues/273

PR: 287888
MFH: 2025Q3
(cherry picked from commit 1e65f0c34b8116718c2c4cfd879a4bc20dcd8ff3)