zilencer: Drop the index from RemotePushDeviceToken.user_id.

The index isn't used, because our unique_index entries provide better
indexes for the queries.

zilencer/migrations/0025_alter_remotepushdevicetoken_user_id_drop_index.py

@@ -0,0 +1,18 @@
+# Generated by Django 3.2.12 on 2022-03-10 12:34
+
+from django.db import migrations, models
+
+
+class Migration(migrations.Migration):
+
+    dependencies = [
+        ("zilencer", "0024_remotepushdevicetoken_user_uuid"),
+    ]
+
+    operations = [
+        migrations.AlterField(
+            model_name="remotepushdevicetoken",
+            name="user_id",
+            field=models.BigIntegerField(null=True),
+        ),
+    ]

zilencer/models.py

@@ -63,7 +63,7 @@ class RemotePushDeviceToken(AbstractPushDeviceToken):
 
     server: RemoteZulipServer = models.ForeignKey(RemoteZulipServer, on_delete=models.CASCADE)
     # The user id on the remote server for this device
-    user_id: int = models.BigIntegerField(db_index=True, null=True)
+    user_id: int = models.BigIntegerField(null=True)
     user_uuid: UUID = models.UUIDField(null=True)
 
     class Meta: