Saints Josaphat and Barlaam never had an official decree of canonization. That process didn't exist (in its earliest form) until 1170 AD. Saints before that were generally just acclaimed by the Christians in the area and probably recognized by a local bishop.
The Vatican does keep a "Roman Martyrology" by which they try to keep a list of all known saints, but the saints that existed before the canonization process are known as "pre-congregation" saints and our certainty about them is generally less, well, certain.
In this case, these two names were removed from the Martyrology. That isn't to say that the Vatican has declared they are not saints, but is no longer actively making that claim.
There have been quite a few other pre-congregation names removed from the list when historical study has found little evidence of their existence or life story.