Fix download path

[horheynm]

Before: .../stub/directory/directory/model.onnx
After: .../stub/directory/model.onnx

Unblocks neuralmagic/deepsparse#1247

epsparse$ pytest '/home/george/nm/deepsparse/tests/utils/test_engine_mocking.py'
============================= test session starts ==============================
platform linux -- Python 3.8.10, pytest-7.4.2, pluggy-1.3.0
rootdir: /home/george/nm/deepsparse
configfile: pyproject.toml
plugins: flaky-3.7.0
collected 7 items                                                              

tests/utils/test_engine_mocking.py .......                               [100%]

=============================== warnings summary ===============================
../../../../usr/lib/python3/dist-packages/requests/__init__.py:89
  /usr/lib/python3/dist-packages/requests/__init__.py:89: RequestsDependencyWarning: urllib3 (2.0.5) or chardet (3.0.4) doesn't match a supported version!
    warnings.warn("urllib3 ({}) or chardet ({}) doesn't match a supported "

../../.local/lib/python3.8/site-packages/urllib3/poolmanager.py:315: 4 warnings
tests/utils/test_engine_mocking.py: 7 warnings
  /home/george/.local/lib/python3.8/site-packages/urllib3/poolmanager.py:315: DeprecationWarning: The 'strict' parameter is no longer needed on Python 3+. This will raise an error in urllib3 v2.1.0.
    warnings.warn(

-- Docs: https://docs.pytest.org/en/stable/how-to/capture-warnings.html
======================== 7 passed, 12 warnings in 3.96s ========================
(.venv) george@quad-mle-2:~/nm/deepsparse$