Don't store default edition in the dataase

bookwyrm/tests/models/test_book_model.py

@@ -84,9 +84,3 @@ class Book(TestCase):
         self.first_edition.description = "hi"
         self.first_edition.save()
         self.assertEqual(self.first_edition.edition_rank, 1)
-
-        # default edition
-        self.work.default_edition = self.first_edition
-        self.work.save()
-        self.first_edition.refresh_from_db()
-        self.assertEqual(self.first_edition.edition_rank, 20)

bookwyrm/tests/models/test_readthrough_model.py

@@ -2,7 +2,7 @@
 from django.test import TestCase
 from django.core.exceptions import ValidationError
 
-from bookwyrm import models, settings
+from bookwyrm import models
 
 
 class ReadThrough(TestCase):
@@ -19,8 +19,6 @@ class ReadThrough(TestCase):
         self.edition = models.Edition.objects.create(
             title="Example Edition", parent_work=self.work
         )
-        self.work.default_edition = self.edition
-        self.work.save()
 
         self.readthrough = models.ReadThrough.objects.create(
             user=self.user, book=self.edition