s390/tape: fix comment typo

Remove duplicated `that' in a comment

Signed-off-by: Jason Wang <wangborong@cdjrlc.com>
Link: https://lore.kernel.org/r/20220715053838.5005-1-wangborong@cdjrlc.com


[agordeev@linux.ibm.com rephrased commit message]
Signed-off-by: Alexander Gordeev <agordeev@linux.ibm.com>