The KB describes on the steps to clear the VAMI backup history
VMware vCenter Server 7.x
VMware vCenter Server 8.x
Stop applmgmt service
service-control --stop applmgmt
Move the backup-history.json
mv /storage/applmgmt/backup_restore/backup-history.json /var/tmp/backup-history.json
Start the service
service-control --start applmgmt