Bump coverage from 5.3 to 5.3.1

Bumps [coverage](https://github.com/nedbat/coveragepy) from 5.3 to 5.3.1.
- [Release notes](https://github.com/nedbat/coveragepy/releases)
- [Changelog](https://github.com/nedbat/coveragepy/blob/master/CHANGES.rst)
- [Commits](nedbat/coveragepy@coverage-5.3...coverage-5.3.1)

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

requirements-test.txt

@@ -1,7 +1,7 @@
 # test runs requirements (versions we'll be testing against) - automatically updated by requires.io
 pytest-cov==2.10.1
 pytest-xdist==2.2.0
-coverage==5.3 # pytest-cov
+coverage==5.3.1 # pytest-cov
 boto3==1.16.39
 mirakuru==2.3.0
 port-for==0.4