Update dependency django to v4.2.20 [SECURITY] (#2562)

Co-authored-by: renovate[bot] <29139614+renovate[bot]@users.noreply.github.com>

Author: renovate[bot]

poetry.lock

@@ -18,7 +18,7 @@ celery = "^5.2.2"
 celery-redbeat = "^2.0.0"
 deepdiff = "^6.6.1"
 dj-database-url = "^0.5.0"
-django = "4.2.18"
+django = "4.2.20"
 django-anymail = {extras = ["mailgun"], version = "^11.1"}
 django-cors-headers = "^4.0.0"
 django-countries = "^7.2.1"