Fix CI failure in make old_version_tests

[habema]

The old_version_tests target was failing in CI because it creates a separate Python 3.9 environment (.venv_39) that doesn't inherit dependencies from the main environment. Some tests import from modules that require optional dependencies.

I just added a step to explicitly install all dependencies for the Python 3.9 environment before running the tests.

[habema]

@seratch i see you merged this into #1706 but it still didnt solve the problem.

Perhaps the correct command is this one?

run: UV_PROJECT_ENVIRONMENT=.venv_39 uv sync --python 3.9 --all-extras --all-packages --group dev

Apologies for the confusion, debugging this locally isn't straightforward.