fix: relax restriction on packaging to >=19.0

23.1 was the current version when we first added packaging, which was
why it was chosen.

We don't really need anything except conformance to PEP 508, though.
19.0 was the last time packaging's changelog mentions that PEP, so
that should be good enough.

Author: apotterri

pyproject.toml

@@ -36,7 +36,7 @@ PyYAML = ">=5.3.0"
 inflection = ">=0.3.0"
 importlib-metadata = ">=0.8"
 importlib-resources = "^5.4.0"
-packaging = ">=21.3"
+packaging = ">=19.0"
 # If you include "Django" as an optional dependency here, you'll be able to use poetry to install it
 # in your dev environment. However, doing so causes poetry v1.2.0 to remove it from the virtualenv
 # *created and managed by tox*, i.e. not your dev environment.