Bug 12291:_(followup) Replace the acronym HTML tag with abbr

Bug 12291:_(followup) Replace the acronym HTML tag with abbr

This patch replaces the last occurrence of <acronym> with <abbr>.

To test:
- Apply this patch on top of the first patch and check that
  "grep -r "<acronym" koha-tmpl/*/*/en/*" does not return any hits.

Signed-off-by: Jonathan Druart <jonathan.druart@biblibre.com>
Signed-off-by: Katrin Fischer <katrin.fischer.83@web.de>
Signed-off-by: Tomas Cohen Arazi <tomascohen@gmail.com>
(cherry picked from commit eb2d7db6555abf1a52f8ce96c0370ec09c32bca8)
Signed-off-by: Chris Cormack <chris@bigballofwax.co.nz>