Running test suite modifies a data file

[liammulh]

When I run the test suite multiple times, I see tests/data/gnomAD/json/GnomadCAF get modified. It seems strange to me that a test suite is writing to a test data file.

Steps to reproduce:

• Clone https://github.com/clingen-data-model/gks-metaschema
• Create a virtual environment: python -m venv venv
• Activate the virtual environment: source venv/bin/activate
• Install dependencies: pip install -e .[dev]
• Run the test suite $n$ times: pytest

It's not deterministic, hence needing to run the test suite $n$ times to reproduce.