Remove lemma from roles available to assign.

entries/views.py

@@ -1026,6 +1026,7 @@ def ajax_predefined_preferences(request):
 def ajax_roles(request):
     roles = []
     for role in SemanticRole.objects.order_by('priority'):
+        if role.role != 'Lemma':
             roles.append({"id": role.id, "role": role.role, "priority": role.priority, "color": role.color})
 
     context = {