mate.mate-applets: 1.20.1 -> 1.20.2 (#41546)

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-applets/versions.

These checks were done:

- built on NixOS
- Warning: no invocation of /nix/store/ll379k2bj134fdja5l40wl49d1zzyj5v-mate-applets-1.20.2/bin/mate-cpufreq-selector had a zero exit code or showed the expected version
- Warning: no invocation of /nix/store/ll379k2bj134fdja5l40wl49d1zzyj5v-mate-applets-1.20.2/bin/.mate-cpufreq-selector-wrapped had a zero exit code or showed the expected version
- 0 of 2 passed binary check by having a zero exit code.
- 0 of 2 passed binary check by having the new version present in output.
- found 1.20.2 with grep in /nix/store/ll379k2bj134fdja5l40wl49d1zzyj5v-mate-applets-1.20.2
- directory tree listing: https://gist.github.com/8917b9a2989aa781cfe8f2a3b86c8821
- du listing: https://gist.github.com/867b59527b5cda0652968142a6f9ef54