Bump coverage from 6.3.3 to 6.4

Bumps [coverage](https://github.com/nedbat/coveragepy) from 6.3.3 to 6.4.
- [Release notes](https://github.com/nedbat/coveragepy/releases)
- [Changelog](https://github.com/nedbat/coveragepy/blob/master/CHANGES.rst)
- [Commits](nedbat/coveragepy@6.3.3...6.4)

---
updated-dependencies:
- dependency-name: coverage
  dependency-type: direct:development
  update-type: version-update:semver-minor
...

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

setup.py

@@ -43,7 +43,7 @@
     ],
     extras_require={
         "test": [
-            "coverage==6.3.3",
+            "coverage==6.4",
             "pytest<7.2",
             "pytest-cov==3.0.0",
             "testfixtures==6.18.5",