Bug 29758: Get rid of warning in members/boraccount.pl

Bug 29758: Get rid of warning in members/boraccount.pl

This patch removes a noisy warning found in production logs.

To test:
1. Run:
   $ tail -f /var/log/koha/kohadev/plack-intranet-error.log
2. Open the 'Accounting' tab for a patron, then click on 'Transactions'
=> FAIL: You see this kind of warning in the logs:

[WARN] CGI::param called in list context from...
3. Apply this patch
4. Repeat 2 (change tab and go back)
=> SUCCESS: No more warning!
5. Sign off :-D

Signed-off-by: Tomas Cohen Arazi <tomascohen@theke.io>
Signed-off-by: David Nind <david@davidnind.com>
Signed-off-by: Jonathan Druart <jonathan.druart@bugs.koha-community.org>
Signed-off-by: Fridolin Somers <fridolin.somers@biblibre.com>