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

cmd/platform/channel.go

@@ -166,7 +166,7 @@ func removeUserFromChannel(channel *model.Channel, user *model.User, userArg str
 		CommandPrintErrorln("Can't find user '" + userArg + "'")
 		return
 	}
-	if err := app.RemoveUserFromChannel(user.Id, "", channel, utils.GetSiteURL()); err != nil {
+	if err := app.RemoveUserFromChannel(user.Id, "", channel); err != nil {
 		CommandPrintErrorln("Unable to remove '" + userArg + "' from " + channel.Name + ". Error: " + err.Error())
 	}
 }