Build(deps): Bump coverage from 5.0.4 to 5.1

Bumps [coverage](https://github.com/nedbat/coveragepy) from 5.0.4 to 5.1.
- [Release notes](https://github.com/nedbat/coveragepy/releases)
- [Changelog](https://github.com/nedbat/coveragepy/blob/master/CHANGES.rst)
- [Commits](nedbat/coveragepy@coverage-5.0.4...coverage-5.1)

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

requirements/ci-wheel.txt

@@ -1,5 +1,5 @@
 -r flake.txt
-coverage==5.0.4
+coverage==5.1
 pytest==5.3.5
 pytest-asyncio==0.10.0
 pytest-cov==2.8.1