Bug 24676: Remove <p/> typo in opac-auth.tt

Bug 24676: Remove <p/> typo in opac-auth.tt

This patch removes some trivial invalid HTML from opac-auth.tt

Test plan:
1. Apply patch
2. As an unauthenticated user, try to place a hold on a search result
e.g. http://localhost:8080/cgi-bin/koha/opac-reserve.pl?biblionumber=29
3. View source or use an inspector to see there is no <p></p> block
between <input type="submit" value="Log in" class="btn"> and
<div id="nologininstructions">

Signed-off-by: Sally <sally.healey@cheshiresharedservices.gov.uk>
Signed-off-by: Martin Renvoize <martin.renvoize@ptfs-europe.com>