PLT-5745 Cleaning up duplicate calls (#7298)

* PLT-5745 Cleaning up duplicate calls

* Fixing missing calls

* Fixing broken test

api4/channel.go

@@ -141,7 +141,7 @@ func updateChannel(c *Context, w http.ResponseWriter, r *http.Request) {
 		return
 	} else {
 		if oldChannelDisplayName != channel.DisplayName {
-			if err := app.PostUpdateChannelDisplayNameMessage(c.Session.UserId, channel.Id, c.Params.TeamId, oldChannelDisplayName, channel.DisplayName); err != nil {
+			if err := app.PostUpdateChannelDisplayNameMessage(c.Session.UserId, channel, oldChannelDisplayName, channel.DisplayName); err != nil {
 				l4g.Error(err.Error())
 			}
 		}