Fixed a pyflakes issue.

- Legacy-Id: 16955

ietf/utils/management/commands/fix_ambiguous_timestamps.py

@@ -8,7 +8,6 @@ import sys
 
 from django.apps import apps
 from django.conf import settings
-from django.contrib.contenttypes.models import ContentType
 from django.core.management.base import BaseCommand
 from django.db import models
 
@@ -62,4 +61,4 @@ class Command(BaseCommand):
                 for field in model._meta.fields:
                     if isinstance(field, models.DateTimeField):
                         self.fixup(model, field.name, start, stop)
-                        
+