xz: upgrade 5.4.5 -> 5.4.6

xz: upgrade 5.4.5 -> 5.4.6

Project has made changes to the site structure: https://tukaani.org/
| The XZ projects were moved to their own website on xz.tukaani.org in
| January 2024. The old links will be kept working via redirections.

While old release tarballs are still being accesible on the site via
redirects, new releases are no longer hosted on the site and point
directly to github - update SRC_URI.

The website change was mentioned in the COPYING file, changing its hash.

Full Changelog:
https://github.com/tukaani-project/xz/releases/tag/v5.4.6

License-Update: new URL due to website restructure

Signed-off-by: Denys Dmytriyenko <denis@denix.org>
Signed-off-by: Richard Purdie <richard.purdie@linuxfoundation.org>