Update depth_helper.py

[portanz]

Summary

This PR allows NixOS users to fetch the model and use it.

wallpaper_depth's setup step does pip install --only-binary=:all: numpy onnxruntime Pillow into a venv. On NixOS there's no FHS (/lib, /usr/lib) for those pre-built manylinux wheels to find shared libs like libstdc++.so.6, libgcc_s.so.1, libgomp.so.1 at import time, so pip install succeeds but import numpy, onnxruntime, PIL fails right after, and setup reports failure.

Motivation

Type of Change

• Bug fix
• New feature
• Breaking change
• Refactoring
• Build / packaging

Related Issue

Testing

noctalia msg panel-toggle noctalia/wallpaper_depth:manager
I tested all the features, including downloading the model, clearing the cache and regenerating masks.

Manual Coverage

• Tested on Niri
• Tested on Hyprland
• Tested on Sway
• Tested on another compositor:
• Tested with different bar positions and density settings
• Tested at different interface scaling values
• Tested with multiple monitors

Screenshots / Videos

Checklist

• This PR is ready for review, or it is marked as Draft.
• I self-reviewed the changes.
• I added or updated translations/en.json, or this PR adds no new user-facing strings.
• I did not edit non-English translation files unless this PR is explicitly for translation tooling, an import/export sync, or a maintainer-requested locale change.

Additional Notes

[VuiMuich]

Can confirm this fixes the issue for me.
(Tested on umbriel)