tests/contrib/django: use proper mock

The read mock should take at least an argument. Fixes:

tests.contrib.django.fixtures.TempStoreClient:client.py:151
  Can't capture request body: test_post_read_error_logging.<locals>.read()
  takes 0 positional arguments but 1 was given

Assisted-by: Cursor

Author: xrmx

tests/contrib/django/django_tests.py

@@ -572,7 +572,7 @@ def test_post_raw_data(django_elasticapm_client):
 def test_post_read_error_logging(django_elasticapm_client, caplog, rf):
     request = rf.post("/test", data="{}", content_type="application/json")
 
-    def read():
+    def read(*args, **kwargs):
         raise IOError("foobar")
 
     request.read = read