mate.mate-desktop: 1.20.1 -> 1.20.3 (#41548)

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-desktop/versions.

These checks were done:

- built on NixOS
- Warning: no invocation of /nix/store/wxcn9xjdga9v1qlsk99rhiaim6xwrkcl-mate-desktop-1.20.3/bin/mate-color-select had a zero exit code or showed the expected version
- /nix/store/wxcn9xjdga9v1qlsk99rhiaim6xwrkcl-mate-desktop-1.20.3/bin/mate-about passed the binary check.
- Warning: no invocation of /nix/store/wxcn9xjdga9v1qlsk99rhiaim6xwrkcl-mate-desktop-1.20.3/bin/.mate-color-select-wrapped had a zero exit code or showed the expected version
- /nix/store/wxcn9xjdga9v1qlsk99rhiaim6xwrkcl-mate-desktop-1.20.3/bin/.mate-about-wrapped passed the binary check.
- 2 of 4 passed binary check by having a zero exit code.
- 0 of 4 passed binary check by having the new version present in output.
- found 1.20.3 with grep in /nix/store/wxcn9xjdga9v1qlsk99rhiaim6xwrkcl-mate-desktop-1.20.3
- directory tree listing: https://gist.github.com/31f847260d9910561df955f376feb063
- du listing: https://gist.github.com/2b921cbfb4bda4b008a2b2a496b49229