Bump coveralls from 2.0.0 to 2.1.0 (#1250)

Bumps [coveralls](https://github.com/coveralls-clients/coveralls-python) from 2.0.0 to 2.1.0.
- [Release notes](https://github.com/coveralls-clients/coveralls-python/releases)
- [Changelog](https://github.com/coveralls-clients/coveralls-python/blob/master/CHANGELOG.md)
- [Commits](TheKevJames/coveralls-python@2.0.0...2.1.0)

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

Co-authored-by: dependabot-preview[bot] <27856297+dependabot-preview[bot]@users.noreply.github.com>

requirements-dev.txt

@@ -1,5 +1,5 @@
 black==19.10b0
-coveralls==2.0.0
+coveralls==2.1.0
 ddt==1.4.1
 flake8-import-order==0.18.1
 pytest==5.4.3