Change Details

Removed obsolete ifdefs Updated History.md.

Moved pre-processor ifdef conditions from `EvtPHOTOS` class to `EvtExternalGenList`. This is associated with T250 and [!17](https://gitlab.cern.ch/evtgen/evtgen/-/merge_requests/17).

Removed obsolete ifdefs Moved pre-processor ifdef conditions from `EvtPHOTOS` class to `EvtExternalGenList`. This is associated with T250 and [!17](https://gitlab.cern.ch/evtgen/evtgen/-/merge_requests/17). Updated History.md.