Bump packaging from 20.9 to 21.0

Bumps [packaging](https://github.com/pypa/packaging) from 20.9 to 21.0.
- [Release notes](https://github.com/pypa/packaging/releases)
- [Changelog](https://github.com/pypa/packaging/blob/main/CHANGELOG.rst)
- [Commits](pypa/packaging@20.9...21.0)

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

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

Author: dependabot[bot]

dev-requirements.txt

@@ -16,7 +16,7 @@ iniconfig==1.1.1
 isort==5.7.0
 mccabe==0.6.1
 mypy-extensions==0.4.3
-packaging==20.9; python_version >= '2.7' and python_version not in '3.0, 3.1, 3.2, 3.3'
+packaging==21.0; python_version >= '2.7' and python_version not in '3.0, 3.1, 3.2, 3.3'
 pathspec==0.8.1
 pluggy==0.13.1; python_version >= '2.7' and python_version not in '3.0, 3.1, 3.2, 3.3'
 py==1.10.0; python_version >= '2.7' and python_version not in '3.0, 3.1, 3.2, 3.3'