SoftBody3D cannot be set to masses with fractional values

### Tested versions

v4.5.1.stable.official [f62fdbde1]

### System information

Godot v4.5.1.stable - Windows 11 (build 26200) - Multi-window, 2 monitors - OpenGL 3 (Compatibility) - NVIDIA T1000 8GB (NVIDIA; 32.0.15.7344) - Intel(R) Core(TM) i7-14700 (28 threads) - 15.69 GiB memory

### Issue description

For some reason, SoftBody3D.total_mass cannot be set to a non-integral value. If you set it to any value with a fractional amount (.1, 3.5, 4.7, etc), it is rounded to the nearest integer plus .01.

### Steps to reproduce

Create a new Godot project. Create a 3D scene. Add a SoftBody3D to the scene. Set it's mass to a positive value with a fractional part.

### Minimal reproduction project (MRP)

[soft-body-mass-bug.zip](https://github.com/user-attachments/files/23319350/soft-body-mass-bug.zip)