Revision: remove salt field.

It's not really needed. More information in the respective change
in the js client.

django_etebase/migrations/0020_remove_collectionitemrevision_salt.py

@@ -0,0 +1,17 @@
+# Generated by Django 3.0.3 on 2020-06-26 08:19
+
+from django.db import migrations
+
+
+class Migration(migrations.Migration):
+
+    dependencies = [
+        ('django_etebase', '0019_auto_20200626_0748'),
+    ]
+
+    operations = [
+        migrations.RemoveField(
+            model_name='collectionitemrevision',
+            name='salt',
+        ),
+    ]