Fix highlight_updated causing errors

[mubinulhaque]

It seems that both XRToolsSnapZone and XRToolsPickable have a signal called highlight_updated. I had mistakenly assumed that only the latter had the signal, which meant that the highlight classes were connecting to these signals and trying to cast the Snap Zones as Pickables, as shown below:

ERROR: core/object/object.cpp:1249 - Error calling from signal 'highlight_updated' to callable: 'MeshInstance3D(highlight_ring.gd)::_on_highlight_updated': Cannot convert argument 1 from Object to Object.

I have now corrected the typing in the signals to instead have the pickable as Node3D, rather than XRToolsPickable.

Testing

The Pickables demo had no issues not present in master. Reloading the project with this scene now no longer causes errors.

Disclaimer

No generative AI was used to enhance or create the code given here.

[mubinulhaque]

A quick code search shows that the first parameter pickable of the highlight_updated signal is never used. Would it be worth removing, or is it intended for users?