Update pytest-cov requirement from <6.0,>=4 to >=4,<7.0

Updates the requirements on [pytest-cov](https://github.com/pytest-dev/pytest-cov) to permit the latest version.
- [Changelog](https://github.com/pytest-dev/pytest-cov/blob/master/CHANGELOG.rst)
- [Commits](pytest-dev/pytest-cov@v4.0.0...v6.0.0)

---
updated-dependencies:
- dependency-name: pytest-cov
  dependency-type: direct:production
...

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

pyproject.toml

@@ -102,7 +102,7 @@ license = { text = "BSD 3-Clause License" }
 [project.optional-dependencies]
 test = [
   "pytest>=6.2.4,<8.4.0",
-  "pytest-cov>=4,<6.0",
+  "pytest-cov>=4,<7.0",
   "pytest-xdist>=3.1",
   "pyyaml>=6,<7",
   "diff-cover>=7.3",