Hi, Normally, in all offer letters, there will be a clause as below or a similar clause:
"This offer is valid until ____ only, and your failure to report to duty on or before _____ will lead to the cancellation of this offer without any further communication."
If any such clause is already added in your offer letter, there is no need for a separate offer cancellation email. If the candidate fails to join on the stipulated date, the offer will be automatically canceled.