Bug 15686: Rename "item level holds" circ rule column to "OPAC item level holds"

Bug 15686: Rename "item level holds" circ rule column to "OPAC item level holds"

This patch changes the column heading on smart-rules.pl to indicate that it only effects item level holds on the OPAC side, rather than the intranet.
To test:
1. Go to Administration, circulation and fine rules.
2. Observe incorrect heading on both the top and bottom of the table.
3. Apply the patch.
4. Repeat step 1.
5. Observe new headings.

Signed-off-by: Liz Rea <wizzyrea@gmail.com>
Signed-off-by: Katrin Fischer <katrin.fischer.83@web.de>
Signed-off-by: Martin Renvoize <martin.renvoize@ptfs-europe.com>