Bump coverage from 4.5.3 to 4.5.4

Bumps [coverage](https://github.com/nedbat/coveragepy) from 4.5.3 to 4.5.4.
- [Release notes](https://github.com/nedbat/coveragepy/releases)
- [Changelog](https://github.com/nedbat/coveragepy/blob/master/CHANGES.rst)
- [Commits](nedbat/coveragepy@coverage-4.5.3...coverage-4.5.4)

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

requirements-test.txt

@@ -1,5 +1,5 @@
 # test runs requirements (versions we'll be testing against) - automatically updated by requires.io
-coverage==4.5.3 # pytest-cov
+coverage==4.5.4 # pytest-cov
 pytest==5.0.1; python_version>'3.4'
 pytest>=4.4.0; python_version<='3.4' # rq.filter: <5.0.0
 port-for==0.4