Bug 32692: Terminology - use staff interface for MARC framework subfield editor

Bug 32692: Terminology - use staff interface for MARC framework subfield editor

For the visibility options in the advanced constraints section of the
MARC framework subfield editor, use 'Staff interface' instead
of 'Intranet'.

This makes it consistent with the terminology list (see
https://wiki.koha-community.org/wiki/Terminology#I).

Test plan:
1. Go to Administration > Catalog > MARC bibliographic framework.
2. Select Actions > MARC structure for any framework.
3. For any tag select Actions > Edit subfields.
4. Note that in the advanced constraints section for the visibility
   field that 'Intranet' is used as an option.
5. Apply the patch.
6. Refresh the page and note that 'Staff interface' is now used, which
   is consistent with the terminology list (see
   https://wiki.koha-community.org/wiki/Terminology#I).
7. Sign off D:

Signed-off-by: David Nind <david@davidnind.com>
Signed-off-by: Amaury GAU <amaury.gau@bulac.fr>
Signed-off-by: Katrin Fischer <katrin.fischer@bsz-bw.de>
Signed-off-by: Tomas Cohen Arazi <tomascohen@theke.io>