Bug 30132: Fix POD, show correct usage of Getopt::Long

Bug 30132: Fix POD, show correct usage of Getopt::Long

the USAGE of overdue_notices.pl shows options such as -date OR
-csv that should be written with double dashes like --date or --csv

Signed-off-by: Katrin Fischer <katrin.fischer.83@web.de>
Signed-off-by: Jonathan Druart <jonathan.druart@bugs.koha-community.org>
Signed-off-by: Fridolin Somers <fridolin.somers@biblibre.com>
Signed-off-by: Kyle M Hall <kyle@bywatersolutions.com>
(cherry picked from commit 0322275a5bce6b849513994d626852fe47ef8ee4)

Signed-off-by: Andrew Fuerste-Henry <andrew@bywatersolutions.com>