If unwanted jobs can be identified by the job names, one can add the names into “Ignore Values” for the SQL Agent alarms. Job names will come up in the “Value” dropdown list in the “Ignore Values…” dialog.
The job failed alarm key includes the time the job failed, therefore to ignore a job one has to include the * character at the end of the name of the job to ignore.
If they are not identified by the job names, then use the Alarm Actions to “Suppress the alarm” where alarm are “SQL Agent…” alarms and the details contain certain words etc. The criteria will be all up to user.