Bug 26111: Add "Serials" (SER) to the reports dictionnary

Bug 26111: Add "Serials" (SER) to the reports dictionnary

It's missing in the template

Test plan:
Go go Home › Reports › Guided reports wizard › Dictionary
At step 2, notice that with this patch you have "Serials" in the
dropdown list (instead of an empty entry)

Signed-off-by: Sally <sally.healey@cheshiresharedservices.gov.uk>
Signed-off-by: Nick Clemens <nick@bywatersolutions.com>
Signed-off-by: Jonathan Druart <jonathan.druart@bugs.koha-community.org>
(cherry picked from commit b0eee4d2e1359050cee3dd23a121e75195b0ce11)

Signed-off-by: Lucas Gass <lucas@bywatersolutions.com>