Bug 30993: Improve translatabilty of UPLOAD av hint

Bug 30993: Improve translatabilty of UPLOAD av hint

Improve translatability on the hint for AV UPLOAD
on the upload tool page.

To test:
* Go to tools > uploads
* Verify that the hint below the 'Browse...' displayes nicely
  and the link to the UPLOAD AV works correctly
* Apply patch
* Verify the link still works and the sentence reads correctly.
  NOTE: now only UPLOAD will be linked.

If you are familiar with the process, you can also make sure
the strings now show up on po files as expected:
https://wiki.koha-community.org/wiki/Translating_Koha#Updating_the_po_files_in_your_installation

Signed-off-by: Caroline Cyr La Rose <caroline.cyr-la-rose@inlibro.com>
Signed-off-by: Kyle M Hall <kyle@bywatersolutions.com>
Signed-off-by: Tomas Cohen Arazi <tomascohen@theke.io>