In PhysicalBone3D, joint constraints properties' description empty

### Tested versions

-Reproducible in: v4.6.dev4.mono.official [bd2ca13c6], v4.5.1.stable.mono.official [f62fdbde1], v4.4.1.stable.mono.official [49a5bc7b6], v3.6.2.stable.mono.official [3cd3caab6]

### System information

Godot v4.5.1.stable.mono - Windows 11 (build 26100) - Multi-window, 1 monitor - Vulkan (Forward+) - dedicated NVIDIA GeForce RTX 4070 Ti SUPER (NVIDIA; 32.0.15.8129) - AMD Ryzen 7 9700X 8-Core Processor (16 threads) - 31.11 GiB memory

### Issue description

Joint constraints properties' description empty on a PhysicalBone3D

**_What's not working?_**
The Joint constraints properties don't have a description when the ones on a standalone joint do

**_Expected?_**
To see the same description shown when you hover the properties of the same type of joint **but when it is a node by itself**

"_No description available._"

### Steps to reproduce

1. Create PhysicalBone3D
2. Select any joint type in the **[Joint]** group
3. In **[Joint Constraints]**, hover over any properties and see the emptiness of its soul

### Minimal reproduction project (MRP)

N/A

Start by comparing the PhysicalBone3D Joint Constraints properties with the corresponding standalone joint node properties and their editor descriptions. Reproduce the issue in the Godot editor by hovering those properties, then confirm that the PhysicalBone3D entries show the same descriptions as the matching joint properties.

Written by the indexing model from the issue text.