fix isort after flake8

src/pretix/base/forms/questions.py

@@ -48,9 +48,7 @@ from django.conf import settings
 from django.contrib import messages
 from django.core.exceptions import ValidationError
 from django.core.files.uploadedfile import SimpleUploadedFile
-from django.core.validators import (
-    MaxValueValidator, MinValueValidator,
-)
+from django.core.validators import MaxValueValidator, MinValueValidator
 from django.db.models import QuerySet
 from django.forms import Select, widgets
 from django.forms.widgets import FILE_INPUT_CONTRADICTION