Remove explicit Django versions from trove classifiers

Not purely a Django package so these don't make that much sense, also
our tests support at least >=2.0, the actual source code probably even a
much much earlier version.

Author: ruohola

pyproject.toml

@@ -20,9 +20,6 @@ classifiers = [
     "Environment :: Plugins",
     "Environment :: Web Environment",
     "Framework :: Django",
-    "Framework :: Django :: 2.2",
-    "Framework :: Django :: 3.2",
-    "Framework :: Django :: 4.0",
     "Framework :: FastAPI",
     "Intended Audience :: Developers",
     "Intended Audience :: Information Technology",