x11-libs/libva is slotted so the dependency should include a slot operator.
Dunno why wine maintainers can't be bothered to look at this in 5 years, but the bug is no longer valid since libva-compat was added.
Sorry, I didn't review all the old bugs after joining wine@ yet -- pretty sure most aren't relevant at this point. In fact, wine doesn't depend on libva anymore.. so this is just obsolete.