Seen: don't use ModificationDateTimeField

this is so we can set it properly in an import script

seen/models.py

@@ -1,8 +1,6 @@
 from django.db import models
 from django.utils import timezone
 
-from django_extensions.db.fields import ModificationDateTimeField
-
 
 class SeenNick(models.Model):
 
@@ -12,7 +10,7 @@ class SeenNick(models.Model):
     channel = models.CharField(max_length=64)
 
     host = models.CharField(max_length=255)
-    seen_time = ModificationDateTimeField(editable=True)
+    seen_time = models.DateTimeField(default=timezone.now)
     what = models.TextField()
 
     class Meta: