Bug 16634: Translatability: Fix issue in memberentrygen.tt

Bug 16634: Translatability: Fix issue in memberentrygen.tt

This patch fixes a small translatability issue in
koha-tmpl/intranet-tmpl/prog/en/modules/members/memberentrygen.tt
The sentence following sentence was splitted by HTML tags:
"Attribute value xxxxx is already in use by another patron record."

To test:
- Review code
- Apply patch
- In Admin, create a unique patron attribute type and try to give
  two patrons the same value for this attribute type.

Signed-off-by: Rocio Dressler <rocio@bywatersolutions.com>
Signed-off-by: Jonathan Druart <jonathan.druart@bugs.koha-community.org>
Signed-off-by: Kyle M Hall <kyle@bywatersolutions.com>