Bug 27876: changed Your tags title to caption in OPAC

Bug 27876: changed Your tags title to caption in OPAC

On the tags page, changed the <h2> "Your tags" to a <caption> to reduce
heading redundancy but keep the information available.

To test:
1) Apply patch
2) Go to OPAC
3) Go to opac-tags.pl
4) Ensure that there is a caption above the table that says "Your tags"
and that it is not a heading tag

Sponsored-by: Catalyst IT
Signed-off-by: Henry Bolshaw <bolshawh@parliament.uk>
Signed-off-by: Nick Clemens <nick@bywatersolutions.com>
Signed-off-by: Jonathan Druart <jonathan.druart@bugs.koha-community.org>
Signed-off-by: Jonathan Druart <jonathan.druart@bugs.koha-community.org>