libdrm: 2.4.90 -> 2.4.91

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

This update was made based on information from https://repology.org/metapackage/libdrm/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 2.4.91 with grep in /nix/store/rff4bpz0j9w5fgxsd5qq1vdv5wpdlwxy-libdrm-2.4.91
- directory tree listing: https://gist.github.com/c13751993f64b3543f93979f9450e5d1