Add missing offsetPositionsFirst translation related to Scheduler component

It seems that the messages are missing the mapping for offsetPositionsFirst. Related to - https://github.com/telerik/kendo-angular/issues/4049

https://github.com/telerik/kendo-angular-messages/blob/develop/messages/scheduler/scheduler.bg-BG.yml#L51
![chrome_oW3ksJPW4Q](https://github.com/telerik/kendo-angular/assets/49076727/e4d198b5-03f7-463f-a85f-8702c9f0b0ce)