Fixes https://gitlab.com/nonguix/nonguix/-/issues/224 * *.scm: Use SPDX license identifier and remove obsolete license statement.
* nongnu/packages/printers.scm (hplip-plugin): New variable. Co-authored-by: Kahka <https://gitlab.com/kahka> Signed-off-by: Jonathan Brielmaier <jonathan.brielmaier@web.de>