mate.mate-power-manager: 1.20.2 -> 1.21.0 (#43182)

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-power-manager/versions.

These checks were done:

- built on NixOS
- /nix/store/3p5n72sk436hkj88ndbws85n3sjpjws6-mate-power-manager-1.21.0/bin/mate-power-manager passed the binary check.
- /nix/store/3p5n72sk436hkj88ndbws85n3sjpjws6-mate-power-manager-1.21.0/bin/mate-power-preferences passed the binary check.
- /nix/store/3p5n72sk436hkj88ndbws85n3sjpjws6-mate-power-manager-1.21.0/bin/mate-power-statistics passed the binary check.
- /nix/store/3p5n72sk436hkj88ndbws85n3sjpjws6-mate-power-manager-1.21.0/bin/.mate-power-manager-wrapped passed the binary check.
- /nix/store/3p5n72sk436hkj88ndbws85n3sjpjws6-mate-power-manager-1.21.0/bin/.mate-power-preferences-wrapped passed the binary check.
- /nix/store/3p5n72sk436hkj88ndbws85n3sjpjws6-mate-power-manager-1.21.0/bin/.mate-power-statistics-wrapped passed the binary check.
- /nix/store/3p5n72sk436hkj88ndbws85n3sjpjws6-mate-power-manager-1.21.0/bin/mate-power-backlight-helper passed the binary check.
- 7 of 7 passed binary check by having a zero exit code.
- 2 of 7 passed binary check by having the new version present in output.
- found 1.21.0 with grep in /nix/store/3p5n72sk436hkj88ndbws85n3sjpjws6-mate-power-manager-1.21.0
- directory tree listing: https://gist.github.com/1e52186ae9e0f46684d551318ba77db0
- du listing: https://gist.github.com/c94ea5d841ae308a842d899ce7685a0b