Fix a migration that could never have run successfully

You can't drop the last column in a table.  I don't understand what
Django was thinking in generating this migration. I hope we don't need
the drop-columns for backward migrations.

setup.py

@@ -29,7 +29,7 @@ package_data = dict(
 
 setup(
     name = "django-wiki",
-    version = "0.0.4",
+    version = "0.0.5",
     author = "Benjamin Bach",
     author_email = "benjamin@overtag.dk",
     description = ("A wiki system written for the Django framework."),

wiki/migrations/0002_remove_article_subscription.py

@@ -12,14 +12,6 @@ class Migration(migrations.Migration):
     ]
 
     operations = [
-        migrations.RemoveField(
-            model_name='articlesubscription',
-            name='articleplugin_ptr',
-        ),
-        migrations.RemoveField(
-            model_name='articlesubscription',
-            name='subscription_ptr',
-        ),
         migrations.DeleteModel(
             name='ArticleSubscription',
         ),