Bump coverage from 5.2 to 5.2.1

Bumps [coverage](https://github.com/nedbat/coveragepy) from 5.2 to 5.2.1.
- [Release notes](https://github.com/nedbat/coveragepy/releases)
- [Changelog](https://github.com/nedbat/coveragepy/blob/master/CHANGES.rst)
- [Commits](nedbat/coveragepy@coverage-5.2...coverage-5.2.1)

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

requirements-test.txt

@@ -2,7 +2,7 @@
 pytest==5.4.3
 pytest-xdist==1.32.0
 pytest-cov==2.10.0
-coverage==5.2 # pytest-cov
+coverage==5.2.1 # pytest-cov
 rabbitpy==2.0.1
 port-for==0.4
 mirakuru==2.3.0