Add correct permission check

https://docs.pretix.eu/en/latest/development/api/customview.html?highlight=permission#event-settings-view

pretix_public_registrations/views.py

 from django.urls import reverse
+from pretix.base.models import Event
 from pretix.control.views.event import EventSettingsFormView, EventSettingsViewMixin
 
 from .forms import PublicRegistrationsSettingsForm
 
 
 class PublicRegistrationsSettingsView(EventSettingsViewMixin, EventSettingsFormView):
+    model = Event
+    permission = "can_change_settings"
     form_class = PublicRegistrationsSettingsForm
     template_name = "pretix_public_registrations/settings.html"