chore: fixed test

*  fixing a test which was replying on implicit behavior in the choices
   between certificate display behaviors
* lint error

lms/djangoapps/learner_home/test_serializers.py

@@ -522,9 +522,12 @@ def test_with_data(self):
         # ... with a certificate
         input_context = self.create_test_context(input_data.course)
 
-        # ... and some data preemptively gathered
+        # ... and some data preemptively gathered, including a certificate display behavior
         available_date = random_date()
         input_data.course.certificate_available_date = available_date
+        input_data.course.certificates_display_behavior = (
+            CertificatesDisplayBehaviors.END_WITH_DATE
+        )
         cert_url = input_context["cert_statuses"][input_data.course.id][
             "cert_web_view_url"
         ]

openedx/core/djangoapps/models/tests/test_course_details.py

@@ -8,7 +8,6 @@
 import pytest
 import ddt
 from pytz import UTC
-from unittest.mock import patch  # lint-amnesty, pylint: disable=wrong-import-order
 
 from django.conf import settings
 from xmodule.modulestore import ModuleStoreEnum