codecov package upgrade

I am setting up the environment to contribute and I identified that codecov package is outdated. under **reqs/dev.txt** file it is mentioned as **codecov==2.1.12**. But when I verify the package in pypy it is showing as **2.1.13**. for reference: https://pypi.org/project/codecov/#history

If this issues makes sense please assign it to me. I can raise a PR for the same :)

Open reqs/dev.txt and compare the pinned codecov version with the release history linked in the issue. Update the dependency to the intended newer release and verify that the development requirements remain installable; done means the file uses the current agreed codecov version.

Vom Indexierungsmodell aus dem Issue-Text verfasst.