Moved choices inside of a test model per coding style.

Follow up to 3a4558b84f.

tests/model_regress/models.py

@@ -1,12 +1,11 @@
 from django.db import models
 
+
+class Article(models.Model):
     CHOICES = (
         (1, 'first'),
         (2, 'second'),
     )
-
-
-class Article(models.Model):
     headline = models.CharField(max_length=100, default='Default headline')
     pub_date = models.DateTimeField()
     status = models.IntegerField(blank=True, null=True, choices=CHOICES)