Bug 34573: Fix inconsistencies in acquisitions modify vendor title tag

Bug 34573: Fix inconsistencies in acquisitions modify vendor title tag

This patch updates the vendor details template so that the title tag
correctly reflects whether the user is viewing the vendor or modifying
it.

To test, apply the patch and go to Acquisitions.

- Locate a vendor and view the details (supplier.pl?booksellerid=X)
  - The title should read "Vendor X > Acquisitions > Koha"
- Edit the vendor.
  - The title should read "Modify vendor X > Acquisitions > Koha"

Signed-off-by: David Nind <david@davidnind.com>
Signed-off-by: Marcel de Rooy <m.de.rooy@rijksmuseum.nl>
Signed-off-by: Martin Renvoize <martin.renvoize@ptfs-europe.com>