[FOLLOWUP][BUGFIX] Fix failing unit tests

A sprite icon utility was changed a bit with patch
for #62963, but the unit tests were not adapted.
Do that now.

Change-Id: I63e0c233d9a63c452f5c70e53ccef5c1b280639a
Resolves: #62963
Releases: master
Reviewed-on: http://review.typo3.org/34231
Reviewed-by: Christian Kuhn <lolli@schwarzbu.ch>
Tested-by: Christian Kuhn <lolli@schwarzbu.ch>
Reviewed-by: Frank Nägler <typo3@naegler.net>
Tested-by: Frank Nägler <typo3@naegler.net>