rename invalid submission created key

fixes SENTRY-5051241416

scipost_django/submissions/templatetags/submissions_pool.py

@@ -43,7 +43,7 @@ def get_fellow_qualification_expertise_level_display(submission, fellow):
         try:
             q = Qualification.objects.filter(
                 submission__in=submission.thread_full, fellow=fellow
-            ).latest("submission__created")
+            ).latest("submission__submission_date")
             return q.get_expertise_level_display() + " (previous submission)"
         except Qualification.DoesNotExist:
             return ""
@@ -73,7 +73,7 @@ def get_fellow_readiness_status_display(submission, fellow):
         try:
             q = Readiness.objects.filter(
                 submission__in=submission.thread_full, fellow=fellow
-            ).latest("submission__created")
+            ).latest("submission__submission_date")
             return q.get_status_display() + " (previous submission)"
         except Readiness.DoesNotExist:
             return ""