Bump coverage from 5.2.1 to 5.3 (#87)

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-preview[bot] <[email protected]>

Co-authored-by: dependabot-preview[bot] <27856297+dependabot-preview[bot]@users.noreply.github.com>

Author: dependabot-preview[bot]

requirements.txt

@@ -1,7 +1,7 @@
 attrs==20.2.0
 certifi==2020.6.20
 chardet==3.0.4
-coverage==5.2.1
+coverage==5.3
 dataclasses-json==0.5.2
 idna==2.10
 marshmallow==3.7.1