Bug 15236: Better translatibility in "Connect biblio.biblionumber to a MARC subfield"

 Bug 15236: Better translatibility in "Connect biblio.biblionumber to a MARC subfield"

This patch moves html markup out of explanatory sentence in koha2marclinks.tt ("Connect
biblio.biblionumber to a MARC subfield") for better translatability.

To test:

- Apply patch
- Go to Home > Administration < Koha to MARC mapping
  and edit a tag
- Verify that text change makes sense

Signed-off-by: Hector Castro <hector.hecaxmmx@gmail.com>
Rewording Ok for translation purposes

Signed-off-by: Jonathan Druart <jonathan.druart@bugs.koha-community.org>
Signed-off-by: Brendan A Gallagher <brendan@bywatersolutions.com>