Bug 34900: Simplify text of about page license information

Bug 34900: Simplify text of about page license information

This patch simplifies the language describing third-party libraries and
their licenses so that translation are not so complicated.

The patch also removes information about some assets which are no longer
part of Koha.

The license information now lists only the library name, version (if
possible) and license.

To test, apply the patch and go to the about page in the staff
interface. Open the "Licenses" tab and check the content.

Signed-off-by: David Nind <david@davidnind.com>
Signed-off-by: Jonathan Druart <jonathan.druart@bugs.koha-community.org>
Signed-off-by: Katrin Fischer <katrin.fischer@bsz-bw.de>