Bump coverage from 5.5 to 6.5.0

Bumps [coverage](https://github.com/nedbat/coveragepy) from 5.5 to 6.5.0.
- [Release notes](https://github.com/nedbat/coveragepy/releases)
- [Changelog](https://github.com/nedbat/coveragepy/blob/master/CHANGES.rst)
- [Commits](coveragepy/coveragepy@coverage-5.5...6.5.0)

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

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

Author: dependabot[bot]

poetry.lock

@@ -56,7 +56,7 @@ pytest-cov = ">=2.10"
 pytest-env = ">=0.6"
 pytest-snapshot = ">=0.8.0"
 coveralls = ">=2.1"
-coverage = "<6"
+coverage = "<7"
 pyinstaller = ">=3.4"
 sphinx = ">=3.1"
 sphinx_rtd_theme = ">=0.5.0"