Modify migration file to include meta data changes

The OIDCBackChannelLogoutEvent model's meta data was changed in commit
f62a72b. Although this has no effect on the database, Django still
wants to include the meta data in migrations. Since this migration file
isn't yet included in any release, it can be modified, instead of
creating a new migration file only for the meta data change.

helusers/migrations/0002_add_oidcbackchannellogoutevent.py

@@ -1,5 +1,3 @@
-# Generated by Django 3.2.4 on 2021-06-21 05:46
-
 from django.db import migrations, models
 import django.utils.timezone
 
@@ -29,6 +27,8 @@ class Migration(migrations.Migration):
                 ("sid", models.CharField(blank=True, db_index=True, max_length=4096)),
             ],
             options={
+                "verbose_name": "OIDC back channel logout event",
+                "verbose_name_plural": "OIDC back channel logout events",
                 "unique_together": {("iss", "sub", "sid")},
             },
         ),