Bump coverage from 5.5 to 7.6.3

Bumps [coverage](https://github.com/nedbat/coveragepy) from 5.5 to 7.6.3.
- [Release notes](https://github.com/nedbat/coveragepy/releases)
- [Changelog](https://github.com/nedbat/coveragepy/blob/master/CHANGES.rst)
- [Commits](nedbat/coveragepy@coverage-5.5...7.6.3)

---
updated-dependencies:
- dependency-name: coverage
  dependency-type: direct:production
  update-type: version-update:semver-major
...

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

requirements/test.txt

@@ -1,5 +1,5 @@
 # Test dependencies go here.
 -r base.txt
 flake8==4.0.1
-coverage==5.5
+coverage==7.6.3
 factory-boy==3.2.1