Bump coverage from 5.3 to 5.3.1 (#5359)

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](coveragepy/coveragepy@coverage-5.3...coverage-5.3.1)

Signed-off-by: dependabot[bot] <[email protected]>

Co-authored-by: dependabot[bot] <49699333+dependabot[bot]@users.noreply.github.com>

Author: dependabot[bot]

requirements/test.txt

@@ -1,7 +1,7 @@
 
 -r base.txt
 Brotli==1.0.9
-coverage==5.3
+coverage==5.3.1
 cryptography==3.2.1; platform_machine!="i686" and python_version<"3.9" # no 32-bit wheels; no python 3.9 wheels yet
 freezegun==1.0.0
 mypy==0.790; implementation_name=="cpython"