Bug 16468 - Remove last "onclick" from the stage MARC records template

Bug 16468 - Remove last "onclick" from the stage MARC records template

This patch reviseds the stage MARC records template, removing
one more "onclick" attribute from the markup and defining that event in
the script.

This patch also corrects a missing quotation mark in the HTML. I have
done some reindentation to that section.

To test, apply the patch and go to Tools -> Stage MARC records for
import.

- Select a MARC file for import.
- Click the "Upload file" button.
- Click the "Stage for import" button. Your import should be correctly
  staged.

Signed-off-by: Claire Gravely <c.gravely@arts.ac.uk>
Signed-off-by: Jonathan Druart <jonathan.druart@bugs.koha-community.org>
Signed-off-by: Kyle M Hall <kyle@bywatersolutions.com>