finance: fix permissions on submitted statement

jdav_web/finance/admin.py

@@ -121,9 +121,6 @@ class StatementSubmittedAdmin(admin.ModelAdmin):
     def has_add_permission(self, request, obj=None):
         return False
 
-    def has_change_permission(self, request, obj=None):
-        return True
-
     def get_readonly_fields(self, request, obj=None):
         readonly_fields = ['submitted']
         if obj is not None and obj.submitted: