Update codecov to 2.1.5

[pyup-bot]

This PR updates codecov from 2.1.4 to 2.1.5.

Changelog

2.1.5

- [273](https://github.com/codecov/codecov-python/pull/273) Implement retries on Codecov API calls
- [265](https://github.com/codecov/codecov-python/pull/265) Add GitHub Actions CI detection
- [267](https://github.com/codecov/codecov-python/pull/267) Add CODECOV_NAME as default for name

Links

• PyPI: https://pypi.org/project/codecov
• Changelog: https://pyup.io/changelogs/codecov/
• Repo: https://github.com/codecov/codecov-python