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

web/web_test.go

@@ -72,7 +72,7 @@ func TestIncomingWebhook(t *testing.T) {
 	team := &model.Team{DisplayName: "Name", Name: "z-z-" + model.NewId() + "a", Email: "test@nowhere.com", Type: model.TEAM_OPEN}
 	team = ApiClient.Must(ApiClient.CreateTeam(team)).Data.(*model.Team)
 
-	app.JoinUserToTeam(team, user, utils.GetSiteURL())
+	app.JoinUserToTeam(team, user)
 
 	app.UpdateUserRoles(user.Id, model.ROLE_SYSTEM_ADMIN.Id)
 	ApiClient.SetTeamId(team.Id)