singularity: 2.4.5 -> 2.4.6

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

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

These checks were done:

- built on NixOS
- ran ‘/nix/store/0rcn1kn4j7rmr0qn314g28vpa4xf230d-singularity-2.4.6/bin/singularity -h’ got 0 exit code
- ran ‘/nix/store/0rcn1kn4j7rmr0qn314g28vpa4xf230d-singularity-2.4.6/bin/singularity --help’ got 0 exit code
- ran ‘/nix/store/0rcn1kn4j7rmr0qn314g28vpa4xf230d-singularity-2.4.6/bin/singularity help’ got 0 exit code
- found 2.4.6 with grep in /nix/store/0rcn1kn4j7rmr0qn314g28vpa4xf230d-singularity-2.4.6
- directory tree listing: https://gist.github.com/e2f21872e885760acf461b07dd5b4f86