PLT-5900 Removed automatic configuration of SiteURL (#5952)

* Revert "PLT-5765 Passed SiteURL to SendNotifications (#5705)"

This reverts commit a8e68bd890.

* Removed automatic configuration of SiteURL

* Reverted unintentional config changes

* Updated help text

* Added link to docs in Site URL warning

* Fixed merge conflict

app/command_echo.go

@@ -88,7 +88,7 @@ func (me *EchoProvider) DoCommand(args *model.CommandArgs, message string) *mode
 
 		time.Sleep(time.Duration(delay) * time.Second)
 
-		if _, err := CreatePost(post, args.TeamId, true, args.SiteURL); err != nil {
+		if _, err := CreatePost(post, args.TeamId, true); err != nil {
 			l4g.Error(args.T("api.command_echo.create.app_error"), err)
 		}
 	}()