Bump codecov from 2.0.16 to 2.0.21

Bumps [codecov](https://github.com/codecov/codecov-python) from 2.0.16 to 2.0.21.
- [Release notes](https://github.com/codecov/codecov-python/releases)
- [Changelog](https://github.com/codecov/codecov-python/blob/master/CHANGELOG.md)
- [Commits](codecov/codecov-python@v2.0.16...v2.0.21)

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

Author: dependabot-preview[bot]

dev-requirements.txt

@@ -8,7 +8,7 @@ VWS-Python-Mock==2019.12.27.0
 VWS-Test-Fixtures==2019.12.13.1
 autoflake==1.3.1
 check-manifest==0.41
-codecov==2.0.16 # Upload coverage data
+codecov==2.0.21 # Upload coverage data
 doc8==0.8.0
 dodgy==0.2.1  # Look for uploaded secrets
 flake8-commas==2.0.0  # Require silicon valley commas