Bug 13857: Email field for sharing is a bit short

Bug 13857: Email field for sharing is a bit short

The email field for sharing a list with another patron is
a bit short.

To test:
- Make sure OpacAllowSharingPrivateLists is activated
- Create a list in OPAC
- Use the "Share list" link to share with another user
- Check the length of the email field and if you like it
  better with this patch applied

Signed-off-by: Marcel de Rooy <m.de.rooy@rijksmuseum.nl>
Signed-off-by: Tomas Cohen Arazi <tomascohen@gmail.com>
(cherry picked from commit fecffe6ebcd8be44d1ecbc2556a226d8a82f4bd5)
Signed-off-by: Chris Cormack <chris@bigballofwax.co.nz>