Fix build after "Discern between VIRTUAL and ABSTRACT class bindings".

[bruvzg]

Fix build after godotengine/godot#58972.

Note: Also requires godot-headers sync to work. I guess it worth waiting for godotengine/godot#59140, which will also require headers sync (but should not break anything else).

[akien-mga]

Note: Also requires godot-headers sync to work. I guess it worth waiting for godotengine/godot#59140, which will also require headers sync (but should not break anything else).

We've been talking a few times about dropping the godot-headers submodule in this repository and directly vendoring the header and API .json. Might be time to actually do it now so that such changes are easier to coordinate.

[akien-mga]

Thanks!