Bump packaging from 20.8 to 20.9

Bumps [packaging](https://github.com/pypa/packaging) from 20.8 to 20.9.
- [Release notes](https://github.com/pypa/packaging/releases)
- [Changelog](https://github.com/pypa/packaging/blob/main/CHANGELOG.rst)
- [Commits](https://github.com/pypa/packaging/compare/20.8...20.9)

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

requirements/dev.txt

@@ -46,7 +46,7 @@ markupsafe==1.1.1
     # via jinja2
 nodeenv==1.5.0
     # via pre-commit
-packaging==20.8
+packaging==20.9
     # via
     #   -r requirements/docs.in
     #   pallets-sphinx-themes

requirements/docs.txt

@@ -22,7 +22,7 @@ jinja2==2.11.2
     # via sphinx
 markupsafe==1.1.1
     # via jinja2
-packaging==20.8
+packaging==20.9
     # via
     #   -r requirements/docs.in
     #   pallets-sphinx-themes

requirements/tests.txt

@@ -12,7 +12,7 @@ greenlet==1.0.0
     # via -r requirements/tests.in
 iniconfig==1.1.1
     # via pytest
-packaging==20.8
+packaging==20.9
     # via pytest
 pluggy==0.13.1
     # via pytest