DECLARE @jobId uniqueidentifier

-- Obtain the current job identifier that is associated with the PurgeHistory
SELECT @jobId = CAST(current_value AS uniqueidentifier)
FROM msdb.dbo.syspolicy_configuration_internal
WHERE name = N'PurgeHistoryJobGuid'

-- Delete the job identifier association in the syspolicy configuration

DELETE FROM msdb.dbo.syspolicy_configuration_internal
WHERE name = N'PurgeHistoryJobGuid'

-- Delete the offending job
EXEC msdb.dbo.sp_delete_job @job_id = @jobId

-- Re-create the job and its association in the syspolicy configuration table
EXEC msdb.dbo.sp_syspolicy_create_purge_job