Cape Verde

Thank you for the interesting question! I am not aware of any companions of the Prophet (S) who travelled all the way to Cape Verde, especially since most of the early Muslims did not have strong skills with boats. Perhaps this refers to someone else who went there (such as an explorer, trader, migrant, or general) who said something similar, or maybe it refers to someone who stood at a different location and said something similar. 

However, absence of evidence is not proof that it did not happen. Possibly, someone will locate evidence that this happened!