Update dependency django to v6

Author: renovate[bot]

pyproject.toml

@@ -15,7 +15,7 @@ dependencies = [
     "click>=8.1,!=8.2.0",
     "deepdiff>=8.0.0,<9",
     "dj-database-url>=0.5.0,<0.6",
-    "django>=5.2,<5.3",
+    "django>=6,<6.1",
     "django-anymail[mailgun]>=11.1,<12",
     "django-cors-headers>=4.0.0,<5",
     "django-countries>=7.2.1,<8",