Bug 19312: Fix typo in template

Bug 19312: Fix typo in template

This patch fixes a simple typo

Test plan:
1) Go to Administration -> MARC bibliographic framework
2) Select a framework and add plugin unimarc_field_121a.pl to 121 field
3) Open cataloguing screen
4) Go to 121 field and check if for subfield a shows two times the value
   2-dimensional
5) Apply the patch
6) Go to 121 field again and check if it shows 2 different values

Mentored-by: Andreas Roussos <a.roussos@dataly.gr>
Signed-off-by: Bernardo Gonzalez Kriegel <bgkriegel@gmail.com>
Signed-off-by: Katrin Fischer <katrin.fischer.83@web.de>
Signed-off-by: Martin Renvoize <martin.renvoize@ptfs-europe.com>