Bug 35412: Fix incorrect capitalization: Toggle Dropdown

Bug 35412: Fix incorrect capitalization: Toggle Dropdown

This patch corrects incorrect capitalization in the last-borrower
include file. The string his hidden except to screen readers, so visual
confirmation isn't straightforward. Viewing the diff should be enough to
confirm this single character change.

Signed-off-by: David Nind <david@davidnind.com>
Signed-off-by: Victor Grousset/tuxayo <victor@tuxayo.net>
Signed-off-by: Katrin Fischer <katrin.fischer@bsz-bw.de>
(cherry picked from commit cd6aebf849e0333ddc9b15204039e8641e2cc186)
Signed-off-by: Fridolin Somers <fridolin.somers@biblibre.com>