fix: missing style definition for .submit-group

pretalx_musicrate/templates/pretalx_musicrate/submission_base.html

@@ -1,11 +1,13 @@
 {% extends "cfp/event/base.html" %}
 {% load compress %}
 {% load i18n %}
+{% load static %}
 
 {% block title %}{{ submission.title }} ::{% endblock %}
 
-{% block cfp_header %}
+{% block stylesheets %}
     {% compress css %}
+        <link rel="stylesheet" type="text/css" href="{% static "common/css/_forms.css" %}" />
         <style>
             .musicrate-pagination {
                 display: flex;
@@ -21,6 +23,9 @@
             }
         </style>
     {% endcompress %}
+{% endblock %}
+
+{% block cfp_header %}
     {% block submission_header %}
     {% endblock %}
 {% endblock %}