librem: 0.5.2 -> 0.5.3

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

This update was made based on information from https://repology.org/metapackage/librem/versions.

These checks were done:

- built on NixOS
- Warning: no binary found that responded to help or version flags. (This warning appears even if the package isn't expected to have binaries.)
- found 0.5.3 with grep in /nix/store/x20d9fh0yfyzm28p3sghxq01c3f2wrmw-librem-0.5.3
- directory tree listing: https://gist.github.com/b80b5c5f4dc93169cf0cfc46f4306e73