mate.mate-menus: 1.20.1 -> 1.21.0 (#43183)

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-menus/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/3q42pbw9k7jimz7bjskcavl6lic263m5-mate-menus-1.21.0
- directory tree listing: https://gist.github.com/abc03dc52627bfc19e82224f6f78572a
- du listing: https://gist.github.com/45f9a8095638ecb7723fa12bab366074