3D Grid doesn't appear correctly on Forward+

### Tested versions

Godot 4.5.1 stable, 4.5 stable, 4.3 stable and 4.2 stable

### System information

Godot v4.5.1.stable - Linux Mint 22.2 (Zara) on X11 - X11 display driver, Multi-window, 1 monitor - Vulkan (Forward+) - (software emulation on CPU) llvmpipe (LLVM 20.1.2, 256 bits) - AMD Ryzen 7 3700X 8-Core Processor (16 threads) - 15.53 Gio memory

### Issue description

I tried using Godot again on an old PC (version info below) and after creating an empty project, enabling the grid (perspective-> show grid) creates really weird visual artifacts. The x-lines don't always appear, and the z-lines do weird stuff on-screen.

I don't remember it happening with 4.3, although I almost exclusively used it for 2D projects -- this could be an issue with Linux and/or my GPU. As the GPU isn't used, this could be an issue. GPU info:
```bash
$ lspci -v -s $(lspci | grep ' VGA ' | cut -d" " -f 1)
28:00.0 VGA compatible controller: Advanced Micro Devices, Inc. [AMD/ATI] Navi 10 [Radeon RX 5600 OEM/5600 XT / 5700/5700 XT] (rev c1) (prog-if 00 [VGA controller])
Subsystem: Sapphire Technology Limited Radeon RX 5600 XT
Flags: bus master, fast devsel, latency 0, IRQ 11, IOMMU group 18
Memory at d0000000 (64-bit, prefetchable) [size=256M]
Memory at e0000000 (64-bit, prefetchable) [size=2M]
I/O ports at e000 [size=256]
Memory at fcd00000 (32-bit, non-prefetchable) [size=512K]
Expansion ROM at 000c0000 [disabled] [size=128K]
Capabilities:
Kernel modules: amdgpu
```

### Steps to reproduce

- Create a new project with Forward+ Mode
- Go in 3D view
- Move around

### Minimal reproduction project (MRP)

[new-project.tar.gz](https://github.com/user-attachments/files/23316085/new-project.tar.gz)

Start by opening the attached new-project.tar.gz and reproducing the artifact in a new Godot project using Forward+ in the 3D view. Compare grid behavior across the listed Godot versions while moving around, including the reported Linux Mint and software-emulation setup. Done means the X and Z grid lines render consistently, or the issue is narrowed to a reproducible environment-specific case.

Written by the indexing model from the issue text.