mate.mate-settings-daemon: 1.20.3 -> 1.21.0 (#43177)

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

This update was made based on information from https://repology.org/metapackage/mate-settings-daemon/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 1.21.0 with grep in /nix/store/vl1l0mhq9d8rdrsk7x9jlwkm4va2fgkd-mate-settings-daemon-1.21.0
- directory tree listing: https://gist.github.com/147e77ed6eab9ee14d1ce2dd1228a1ec
- du listing: https://gist.github.com/63c6df92545f5c99dbbcce75dcb3f7c5