Revert "[MM-8497] Ability to set Do Not Disturb for a specified period of time (#16067)" (#17657)

This reverts commit 77d42568f9.

app/app.go

@@ -578,7 +578,3 @@ func (a *App) dbHealthCheckKey() string {
 func (a *App) SetServer(srv *Server) {
 	a.srv = srv
 }
-
-func (a *App) UpdateExpiredDNDStatuses() ([]*model.Status, error) {
-	return a.Srv().Store.Status().UpdateExpiredDNDStatuses()
-}