Bug 29216: Correct --where documentation in update_patrons_category.pl

Bug 29216: Correct --where documentation in update_patrons_category.pl

This patch removes two misleading examples of the --where parameter
documentation in update_patrons_category.pl

To test:

1. Apply patch
2. In your favourite text editor, open misc/cronjobs/update_patrons_category.pl
3. Look for the documentation for the --where parameter (around line 133 or so)
4. Make sure the examples and their explanations make sense
5. Sign off :)

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>