todolists: Remove unused ModelManager

todolists/models.py

 from django.contrib.auth.models import User
 from django.contrib.sites.models import Site
 from django.db import models
-from django.db.models import Q
 from django.db.models.signals import pre_save
 
 from main.models import Arch, Repo, Package
 from main.utils import set_created_field
 
 
-class TodolistManager(models.Manager):
-    def incomplete(self):
-        not_done = ((Q(todolistpackage__status=TodolistPackage.INCOMPLETE) |
-                Q(todolistpackage__status=TodolistPackage.IN_PROGRESS)) &
-                Q(todolistpackage__removed__isnull=True))
-        return self.order_by().filter(not_done).distinct()
-
-
 class Todolist(models.Model):
     slug = models.SlugField(max_length=255, unique=True)
     old_id = models.IntegerField(null=True, unique=True)
@@ -27,8 +18,6 @@ class Todolist(models.Model):
     last_modified = models.DateTimeField(editable=False)
     raw = models.TextField(blank=True)
 
-    objects = TodolistManager()
-
     class Meta:
         get_latest_by = 'created'