[REF] im_livechat: remove dummy match_rules() function

introduced in 9 at d2574b7018.

addons/im_livechat/models/im_livechat_channel.py

@@ -200,10 +200,6 @@ class ImLivechatChannel(models.Model):
             info['options']["default_username"] = username
         return info
 
-    # FIXME: to remove in master
-    @api.model
-    def match_rules(self, request, channel_id, username='Visitor'):
-        pass
 
 class ImLivechatChannelRule(models.Model):
     """ Channel Rules