trivial: Fix up some introspection annotations
trivial: Fix up some introspection annotations

Since the GPtrArray container owns its contents and dereferences its
values when freed, transfer:full is actually wrong, as that would
require explicit freeing of the individual values by the caller.
(At least as far as I understand the documentation)

ximion/appstream,ximion/appstream,ximion/appstream,ximion/appstream