Bug 26541: Remove percent sign from discount button

Bug 26541: Remove percent sign from discount button

Realized I'd left a stray tag, fixed.

To test:
1 - go to borrower account, apply manual fee
2 - go to Transactions tab and see that fee has "% Apply discount" button
3 - apply patch, restart, reload page
4 - button just says "Apply discount"

Signed-off-by: David Nind <david@davidnind.com>
Signed-off-by: Katrin Fischer <katrin.fischer.83@web.de>
Signed-off-by: Jonathan Druart <jonathan.druart@bugs.koha-community.org>