rdkafka: 0.11.3 -> 0.11.4

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

This update was made based on information from https://repology.org/metapackage/rdkafka/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 0.11.4 with grep in /nix/store/p7dbh8kabl3bqr28icnkzp55s6636mpl-rdkafka-0.11.4
- directory tree listing: https://gist.github.com/ab8b067a5f31e07af4ed6b1dbdc1a8a4