Bug 11576: Make "manage" translatable - serials-collection

Bug 11576: Make "manage" translatable - serials-collection

If a subscription is irregular, a tab with "manage" is displayed on the
serial collection page.
But this string is not translatable.

Test plan:
1/ Go on the serial collection page of an irregular subscription (or
create one).
2/ Note that the first tab was named "managed", it's now "Manage".
3/ Update a po lang file and confirm you see the string and you are able
to translate it.

Signed-off-by: Bernardo Gonzalez Kriegel <bgkriegel@gmail.com>
Work as described, no koha-qa errors

Signed-off-by: Marcel de Rooy <m.de.rooy@rijksmuseum.nl>
Signed-off-by: Tomas Cohen Arazi <tomascohen@gmail.com>