Fixed #22487: Separated schema migration from data migration in test

The data migration failed on Oracle, killing the entire test suite.

Thanks timo for reporting the Oracle breakage,
and andrewgodwin for suggesting the solution.

tests/migration_test_data_persistence/migrations/0001_initial.py

@@ -4,14 +4,6 @@ from __future__ import unicode_literals
 from django.db import models, migrations
 
 
-def add_book(apps, schema_editor):
-    apps.get_model("migration_test_data_persistence", "Book").objects.using(
-        schema_editor.connection.alias,
-    ).create(
-        title="I Love Django",
-    )
-
-
 class Migration(migrations.Migration):
 
     dependencies = [
@@ -28,7 +20,4 @@ class Migration(migrations.Migration):
             },
             bases=(models.Model,),
         ),
-        migrations.RunPython(
-            add_book,
-        ),
     ]