Bug 10020: Remove code related to ethnicity

Bug 10020: Remove code related to ethnicity

This is a(nother) vestige of Koha (2.2?).
This patch removes unused code related to the 'ethnicity'.

In detail:
There is no way to fill the ethnicity table.
There is no way to fill the borrowers.ethnicity and borrowers.ethnotes.

BUT if borrowers.ethnicity exists, the value is displayed on
members/moremember.pl (and only here).

Test plan:
Apply this patch and confirm there is no regression on
adding/updating/deleting patrons.
Note that you don't see the ethnicity value on the moremember.pl page even if a patron has it.

Signed-off-by: Nick Clemens <nick@quecheelibrary.org>
Signed-off-by: Kyle M Hall <kyle@bywatersolutions.com>
Signed-off-by: Tomas Cohen Arazi <tomascohen@theke.io>