Bug 36961: Fix typo in opacreadinghistory system preference description

Bug 36961: Fix typo in opacreadinghistory system preference description

Fix a spelling error in the opacreadinghistory system preference
description - 'itms' to 'items'.

Test plan:
1. In the staff interface view the description for the
   opacreadinghistory system preferences (Koha administration >
   System preferences > search for opacreadinghistory).
2. Note that it reads "Allow patrons to see what itms they have
   checked out in the past."
3. Apply the patch.
4. Refresh the page.
5. Note that 'itms' is now spelt correctly as 'items'.
6. Sign off.

Signed-off-by: Laura Escamilla <laura.escamilla@bywatersolutions.com>
Signed-off-by: Martin Renvoize <martin.renvoize@ptfs-europe.com>