fargo: add missing migration (#22682)

We set a default to create the new Document.creation_date field but it's
not part of the real models, this migration revert it.

fargo/fargo/migrations/0016_auto_20180330_2248.py

@@ -0,0 +1,20 @@
+# -*- coding: utf-8 -*-
+# Generated by Django 1.11.11 on 2018-03-30 22:48
+from __future__ import unicode_literals
+
+from django.db import migrations, models
+
+
+class Migration(migrations.Migration):
+
+    dependencies = [
+        ('fargo', '0015_document_creation_date'),
+    ]
+
+    operations = [
+        migrations.AlterField(
+            model_name='document',
+            name='creation_date',
+            field=models.DateTimeField(auto_now_add=True),
+        ),
+    ]