Snowflake doesn't support database-level delete (#21961)

Author: timgraham

django_snowflake/features.py

@@ -46,6 +46,9 @@ class DatabaseFeatures(BaseDatabaseFeatures):
     # This feature is specific to the Django fork used for testing.
     supports_limit_in_exists = False
     supports_json_negative_indexing = False
+    supports_on_delete_db_cascade = False
+    supports_on_delete_db_default = False
+    supports_on_delete_db_null = False
     supports_over_clause = True
     supports_partial_indexes = False
     # https://docs.snowflake.com/en/sql-reference/functions-regexp.html#backreferences