Update migration after django update (#1815)

api/funkwhale_api/audio/migrations/0004_alter_channel_metadata.py

@@ -0,0 +1,20 @@
+# Generated by Django 3.2.13 on 2022-06-27 19:15
+
+import django.core.serializers.json
+from django.db import migrations, models
+import funkwhale_api.audio.models
+
+
+class Migration(migrations.Migration):
+
+    dependencies = [
+        ('audio', '0003_channel_rss_url'),
+    ]
+
+    operations = [
+        migrations.AlterField(
+            model_name='channel',
+            name='metadata',
+            field=models.JSONField(blank=True, default=funkwhale_api.audio.models.empty_dict, encoder=django.core.serializers.json.DjangoJSONEncoder, max_length=50000),
+        ),
+    ]