CI test run can be flaky due to exceeding GitHub API limits

[StevenMaude]

The tests in CI do pass without any change. But when running the tests, I did get for one run:

FAILED tests/reports/test_views.py::test_report_view_last_updated - osgithub.github.GithubAPIException: {"message": "API rate limit exceeded for (redacted IP address). (But here's the good news: Authenticated requests get a higher rate limit. Check out the documentation for more details.)", "documentation_url": "https://docs.github.com/rest/overview/resources-in-the-rest-api#rate-limiting"}

The environment variables are configured in the test workflow. The GITHUB_TOKEN environment variable is unset as this commit.

There might be a good reason why we leave this unset, but it's not documented in the commit history or PR thread.

[StevenMaude]

Just happened again, with a run for Dependabot.