Test suite is non-deterministic

[bsweger]

When the test suite runs locally and via CI, the results can vary between runs, even when the inputs haven't changed. The culprit is preprocess_jhu files has expected combinations of location, week

Here's an example of a test failure (running on macos-latest) followed by success on a re-run

1. Attempt one - failure
2. Attempt two - successful re-run

There's an open question of whether or not covidHubUtils needs to keep the data pre-processing functions for target data that is no longer being updated.

If we're keeping these functions and their associated tests, we should fix the cause of this erratic behavior. We might also want to refactor ``preprocess_jhu files has expected combinations of location, week into a true unit test, rather than calling out to external dependencies like `covidData` (the test suite takes me 30 minutes to run locally).

Definition of done:

• re-running covidHubUtils test suite produces consistent results
• covidHubUtils unit tests avoid external calls