Bug 38329: Remove orphan confirm_deletion() in supplier.tt

Bug 38329: Remove orphan confirm_deletion() in supplier.tt

The JavaScript function confirm_deletion() in supplier.tt has either
been an unused orphan since bug 28082 two years ago, or since the switch
from YUI to Bootstrap 12 years ago. Doesn't matter which, nothing calls
it, and if it was called, it would fail by trying to GET with
op="delete" rather than POST with op="cud-delete".

Test plan:
 1. Acquisitions - New vendor, enter a name and Save
 2. Click the name of your new vendor, so your URL is at supplier.pl
 3. Click Delete vendor to verify that deleting still works without this
    unused code which would fail

Sponsored-by: Chetco Community Public Library
Signed-off-by: Owen Leonard <oleonard@myacpl.org>
Signed-off-by: Lucas Gass <lucas@bywatersolutions.com>
Signed-off-by: Katrin Fischer <katrin.fischer@bsz-bw.de>