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

api4/apitestlib.go

@@ -362,7 +362,7 @@ func (me *TestHelper) UpdateActiveUser(user *model.User, active bool) {
 func LinkUserToTeam(user *model.User, team *model.Team) {
 	utils.DisableDebugLogForTest()
 
-	err := app.JoinUserToTeam(team, user, utils.GetSiteURL())
+	err := app.JoinUserToTeam(team, user)
 	if err != nil {
 		l4g.Error(err.Error())
 		l4g.Close()