Bug 18681: Translatability: Get rid of [%% in translation for about.tt

Bug 18681: Translatability: Get rid of [%% in translation for about.tt

Translation tool picks a line
%s [%% IF warnPrefBiblioAddsAuthorities || warnPrefEasyAnalyticalRecords ||
...due to a line break inside a template directive.
This patch fixes it.

To test:
- Update QA tools
  (see https://bugs.koha-community.org/bugzilla3/show_bug.cgi?id=18675#c2)
- Verify that code change makes sense
- Apply patch
- Run QA tools

Followed test plan and everything was as intended
Signed-off-by: Alex Buckley <alexbuckley@catalyst.net.nz>
Signed-off-by: Alex Buckley <alexbuckley@catalyst.net.nz>
Signed-off-by: Jonathan Druart <jonathan.druart@bugs.koha-community.org>