core-deps/AppStream: update to 0.15.5
Supports ignoring warnings due to not supporting GNOME versioning policy.
https://github.com/ximion/appstream/compare/v0.15.4...v0.15.5
Supports ignoring warnings due to not supporting GNOME versioning policy.
https://github.com/ximion/appstream/compare/v0.15.4...v0.15.5