lxqt.lxqt-themes: 0.12.0 -> 0.13.0

Semi-automatic update generated by https://github.com/ryantm/nixpkgs-update tools.

This update was made based on information from https://repology.org/metapackage/lxqt-themes/versions.

These checks were done:

- built on NixOS

- 0 of 0 passed binary check by having a zero exit code.
- 0 of 0 passed binary check by having the new version present in output.
- found 0.13.0 with grep in /nix/store/fs36lbzyd10wzif3mk70hwjqwin8bv7f-lxqt-themes-0.13.0
- directory tree listing: https://gist.github.com/ba1226aef8f1c4dfc1ae26d7a55031f3
- du listing: https://gist.github.com/99abafab17751529577df2cd7d2a12d9