Fix isort issue

src/pretix/control/views/vouchers.py

@@ -50,7 +50,7 @@ from django.http import (
 from django.shortcuts import redirect, render
 from django.urls import resolve, reverse
 from django.utils.functional import cached_property
-from django.utils.html import format_html, escape
+from django.utils.html import escape, format_html
 from django.utils.safestring import mark_safe
 from django.utils.timezone import now
 from django.utils.translation import gettext_lazy as _