Bump coverage from 5.2.1 to 5.3

Bumps [coverage](https://github.com/nedbat/coveragepy) from 5.2.1 to 5.3.
- [Release notes](https://github.com/nedbat/coveragepy/releases)
- [Changelog](https://github.com/nedbat/coveragepy/blob/master/CHANGES.rst)
- [Commits](coveragepy/coveragepy@coverage-5.2.1...coverage-5.3)

Signed-off-by: dependabot[bot] <[email protected]>

Author: dependabot[bot]

requirements_dev.txt

@@ -1,5 +1,5 @@
 bump2version==1.0.0
-coverage==5.2.1
+coverage==5.3
 flake8==3.8.3
 mock==3.0.5
 pip==20.2.2