Remove Django version classifiers

` Django :: 4` is valid but `Django :: 5` is not? No reason to be
specific with versions anyway.

Author: Stormheg

pyproject.toml

@@ -13,8 +13,6 @@ authors = [
 classifiers = [
     "Development Status :: 3 - Alpha",
     "Framework :: Django",
-    "Framework :: Django :: 4",
-    "Framework :: Django :: 5",
     "Framework :: Wagtail",
     "Framework :: Wagtail :: 5",
     "Framework :: Wagtail :: 6",