[TASK] Avoid sysLog calls in MailUtilityTest

Resolves: #57676
Releases: 6.2
Change-Id: I6f694a2c595756595b09aa4a8a91cb795e8a47b7
Reviewed-on: https://review.typo3.org/29192
Reviewed-by: Stefan Neufeind
Tested-by: Stefan Neufeind
Reviewed-by: Oliver Klee
Reviewed-by: Pascal Dürsteler
Reviewed-by: Christian Kuhn
Tested-by: Christian Kuhn