Adjust demo to use Fix XR Body crouching and climbing

[fire]

godotengine/godot#89103

[Malcolmnixon]

The body crouching and climbing change was to Godot and should be available for general use with the Godot 4.3dev5 release.

[fire]

So nothing to do?

[Malcolmnixon]

Shouldn't be. I did some basic checks standing on things and verifying I was able to actually move the avatar up. You may want to confirm with a build of Godot master, or Godot 4.3-dev5 when it comes out, and see if you can find any positioning issues.