black: Reformat with Black 23.

Black 23 enforces some slightly more specific rules about empty line
counts and redundant parenthesis removal, but the result is still
compatible with Black 22.

(This does not actually upgrade our Python environment to Black 23
yet.)

Signed-off-by: Anders Kaseorg <anders@zulip.com>

zilencer/migrations/0013_remove_customer_billing_user.py

@@ -4,7 +4,6 @@ from django.db import migrations
 
 
 class Migration(migrations.Migration):
-
     dependencies = [
         ("zilencer", "0012_coupon"),
     ]