Update coverage requirement from ~=7.3.2 to ~=7.4.0

Updates the requirements on [coverage](https://github.com/nedbat/coveragepy) to permit the latest version.
- [Release notes](https://github.com/nedbat/coveragepy/releases)
- [Changelog](https://github.com/nedbat/coveragepy/blob/master/CHANGES.rst)
- [Commits](nedbat/coveragepy@7.3.2...7.4.0)

---
updated-dependencies:
- dependency-name: coverage
  dependency-type: direct:production
...

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

requirements.txt

@@ -17,4 +17,4 @@ yapf~=0.40.1 # code formatting
 # testing & QA
 pytest~=7.4.3 # testing
 tox~=4.11.4 # testing
-coverage~=7.3.2 # code coverage
+coverage~=7.4.0 # code coverage