Bump pytest-cov from 2.8.1 to 2.9.0

Bumps [pytest-cov](https://github.com/pytest-dev/pytest-cov) from 2.8.1 to 2.9.0.
- [Release notes](https://github.com/pytest-dev/pytest-cov/releases)
- [Changelog](https://github.com/pytest-dev/pytest-cov/blob/master/CHANGELOG.rst)
- [Commits](pytest-dev/pytest-cov@v2.8.1...v2.9.0)

Signed-off-by: dependabot-preview[bot] <support@dependabot.com>

Author: dependabot-preview[bot]

poetry.lock

@@ -26,7 +26,7 @@ cbor2 = "^5.1.0"
 [tool.poetry.dev-dependencies]
 pytest = "^5.4"
 black = {version = "^19.10b0",allow-prereleases = true}
-pytest-cov = "^2.8.1"
+pytest-cov = "^2.9.0"
 numpy = "^1.18.2"
 jsonschema = "^3.2.0"