Remove importlib backport

Rationale: We drop support for Python <3.9

aleksis/core/util/core_helpers.py

-import sys
 from datetime import datetime, timedelta
-from importlib import import_module
+from importlib import import_module, metadata
 from itertools import groupby
 from operator import itemgetter
 from typing import Any, Callable, Optional, Sequence, Union
 
-if sys.version_info >= (3, 9):
-    from importlib import metadata
-else:
-    import importlib_metadata as metadata
-
 from django.conf import settings
 from django.db.models import Model, QuerySet
 from django.http import HttpRequest

pyproject.toml

@@ -89,7 +89,6 @@ psutil = "^5.7.0"
 celery-progress = "^0.1.0"
 django-cachalot = "^2.3.2"
 django-prometheus = "^2.1.0"
-importlib-metadata = {version = "^4.0.0", python = "<3.9"}
 django-model-utils = "^4.0.0"
 bs4 = "^0.0.1"
 django-uwsgi-ng = "^1.1.0"