Bug 15992: Renaming 'Operations' column heading to 'Actions'

Bug 15992: Renaming 'Operations' column heading to 'Actions'

to be consistent with other Administration tables
These actions were already made into buttons so will just make this small string change

To test:

1) Go to Admin -> Item search fields
2) Confirm column heading now reads 'Actions'

Sponsored-by: Catalyst IT
NOTE: Trivial string change, screen refresh confirms change.

Signed-off-by: Mark Tompsett <mtompset@hotmail.com>
Signed-off-by: Jonathan Druart <jonathan.druart@bugs.koha-community.org>
Signed-off-by: Brendan Gallagher brendan@bywatersolutions.com